Updated 19 May 2013:  Today a 5.9 earthquake struck just off the coast of Fukushima, as reported by RT:  Initial reports by TEPCO indicate no abnormalties, but I will post any changes to that here.

Updated 09 May 2013:  Asahi Shimbun reported [archived here if the report "vanishes"] that TEPCO plans on pumping groundwater that surrounds the reactors into the ocean, apparently in a desperate attempt to prevent it from leaking further into the reactor buildings:

• “The company has dug 12 wells to the west of the reactor buildings, where it plans to pump up groundwater before it can enter the facilities and become contaminated.”
  
• “…about 400 tons of groundwater flow into the reactor buildings on a daily basis and mixes with the radioactive water…” –my comment:  That is equivalent to 100,000 gallons of water PER DAY, or enough water to fill an olympic size pool every 6 days leaking into the reactor buildings…(400tons = 800,000 lbs = ~100,000 U.S. Gallons; Olympic size pool = 660,000 gallons)
• “…300 tons of groundwater would still flow into the reactor buildings every day even after TEPCO starts pumping up the water through the wells…”
• “…Currently, surface tanks at the Fukushima No. 1 plant hold about 280,000 tons of radioactive water. An additional 100,000 tons are believed to be flooding the basements of the No. 1 to No. 4 reactor buildings as well as the turbine buildings. (my comment:  Note that is TONS, not pounds….they are in serious trouble)
• “…An estimated 120 tons of radioactive water leaked into the ground from the faulty underground tanks. …”
• “…The underground storage tanks were protected by a double layer of polyethylene waterproof sheets and a 6.4-millimeter-thick sheet of bentonite, a clay-like substance.  The ministry’s standards for controlled disposal sites for industrial waste call for at least 50 centimeters of bentonite to surround the waterproof sheets. TEPCO officials apparently felt that a double layer of polyethylene waterproof sheets would be sufficient…”
• The illustration (embedded in the story) indicates the number of above ground storage containers on site.  Note that the blue cylindrical containers are actually the size of railroad cars, and the silo-type are even bigger.  On the Google Maps below, if you zoom in you can actually see how many of these there are just a few hundred yards from the ocean…WHAT HAPPENS WHEN ANOTHER EARTHQUAKE HITS THAT LOCATION?

Updated 06 Apr 2013:  Reuters – 120 tons of highly radioactive water has leaked from a containment pond (really just a hole dug in the ground and lined with a “water-proof” material) at Fukushima into ground water. READ HERE

Updated 06 Apr 2013:  ”…Children born in Alaska, California, Hawaii, Oregon, and Washington between one week and 16 weeks after the meltdowns began in March 2011 were 28 percent more likely to suffer from congenital hypothyroidism than were kids born in those states during the same period one year earlier, a new study shows….”

Updated 26 Feb 2013:  All stories and info I have personally collected can be found HERE

Update 14 Jan 2013 - The following German scientific research video shows simulation of CS-137 radiation spreading from Fukushima to the west coast of the United States (projected) for a period of 5 years…it shows Hawaii will be diluted in two years:

(http://therabbithold.blogspot.com/2013/01/the-following-german-scientific.html)

Update:  NHK broadcasting released this story 18 June 2012, detailing how the government of Japan hid a map provided to them by the U.S. displaying the spread of radioactivity in the week following the accident.  The broadcast notes that the map “…suggests residents close to the plant were exposed to the annual permissible level within 8 hours...”

Here is a link to the NHK report:  http://www3.nhk.or.jp/daily/english/20120619_01.html

On 28 Oct 2011, the Atmospheric Chemistry and Physics Discussions (ACPD) group released a paper titled “Radionuclide release from Fukushima Nuclear Power Plant”.  This paper details the release of two isotopes, Xenon-133 and Caesium-137 into the atmosphere following the earthquake/tsunami on 11 March 2011.

 Differing from previous maps and projections based upon hypothesis of wind direction and atmospheric conditions, this study looks BACK and can definitively determine the amount of release.  The results are extremely disturbing, not just for Japan, but for Hawaii, Alaska, Canada, the U.S. and really, the entire world.

 Especially disconcerting is the fact that the largest amount of radiation reached the United States within 1 week of the accident.  Do you remember anything about that being told to you by the main-stream press or Government?  And what about the decisions, early on, not to monitor radiation levels in fish, vegetables, and meat in the U.S.?

 Note:  This paper only determined the dispersal of Xenon-133 and Caesium-137.  Other products (such as Iodine) have not been released by governments so they were not included…again…why?

 Below, I have extracted some key data points, and you can view the entire paper HERE

1.  “…In this paper, we determine the emissions of two important radionuclides, the 133 noble gas xenon-133 ( Xe, lifetime of 5.25 days) and the aerosol-bound caesium-137
137 ( Cs, lifetime of 30 yr)…” 

2.  “…Regarding Xe (Xenon-133), we find a total release of 16.7 EBq released, which is the largest radioactive noble gas release in history not associated with nuclear bomb testing.  There is strong evidence that the first strong release started very early, possibly immediately after the earthquake and the emergency shutdown on 11 March at 06:00 UTC. The entire noble gas inventory of reactor units 1–3 was set free into the atmosphere between 11 and 15 March 2011…”

3.  “…regarding Caesium 137 (Cs), the inversion results give a total emission of 35.8 (23.3–50.1) PBq, or about 42 % of the estimated Chernobyl emission…”

4.  “…indicates that emissions were not only coming from the damaged reactor cores, but also from the spent-fuel pool of unit 4…” 

5.  “…While at first sight it seemed fortunate that westerly winds prevailed most of the time during the accident, a different picture emerges from our detailed analysis. Exactly during and following the period of the strongest Cs emissions on 14 and 15 March as well as after another period with strong emissions on 19 March, the radioactive plume was advected over Eastern Honshu Island (Honshu is another name for Japan), where precipitation deposited a large fraction of 137 Cs on land surfaces. The plume was also dispersed quickly over the entire Northern Hemisphere, first reaching North America on 15 March and Europe on 22 March…”

6.  “…There is a larger common spent fuel pool at the site, on ground level. Spent fuel is transferred to this pool after at least 19 months, but the decay heat is large enough to still require active cooling. This pond contained 6375 fuel assemblies.

7.  “…The earthquake triggered the automatic shutdown of the chain reaction in the units 1 to 3 at 05:46 UTC (that is 14:46 Japan Standard Time) on 11 March. Outside power
supply was lost and the emergency diesel generators started up. However, when the tsunami arrived 50 minutes later, it inundated the sites of the reactors and their auxiliary buildings and caused the total loss of AC power, except for one of the three diesel generators of unit 6…”

8.  “…Although at different rates, cooling of the reactor cores was lost, water levels in the reactor pressure vessels could not be maintained, and in all three units that had been under operation, the cores degraded and, as has been reported, partially melted…”

9.  “…The hydrogen produced in this process caused major explosions which massively damaged the upper parts of the reactor buildings of units 1 and 3. Damage to the upper parts of the reactor building could be prevented in unit 2, however, a hydrogen explosion there presumably damaged the suppression chamber…”

10.  “…Cooling was lost as well for the spent fuel ponds, leading to heating up of the water and raising concerns about fuel rods also becoming uncovered there. The information concerning these ponds and possible releases from them is much less clear….”

11.  “…However, it is obvious that the most dangerous situation was in the pond of unit 4, into which the whole core had been unloaded for maintenance work in the reactor. The decay heat for this pool was about 2 MW. A massive hydrogen explosion occurred there which may have been caused by degraded fuel from this pond…”

12.  “…Total Xenon-133 emissions are 16.7 EBz, 1/3 more than the estimated inventory of the site, and 2.5 times the estimated Chernobyl release of 6.5 EBq…”

13.  “The fact that more Xenon-133 was released than was supposed to be on-site can be explained by the possibility that recriticality has occured in one of the reactor units.  Furthermore, noble gas releases may have occured at other Japanese Nuclear Power Plants other than Fukushima…”

14.  “The total amount of Caesium-137 released was 35.8PBq, 34% MORE THAN THE FIRST GUESS, and about 42% of the estimated total Chernobyl emission of 85 PBq…”

15.  “…There were 3 monitoring sites primarily used to collect data on the emissions:  Richland (Washington), Oahu (Hawaii), and Stockholm (Sweden).  At Richland, the plume of Xenon-133 released from Fukushima arrived on 16 March…”

16.  On 12 March, a high pressure system forced winds at Fukushima to shift from WNW to SW.  “…For a few hours around 18:00 UTC on 12 March the coastal areas
north of FD-NPP were affected by the radioactive plume but deposition of radioactive material was limited because no precipitation fell at that time…”

17.  “This plume of Caesum 137 eventually “… produced higher 137 Cs concentrations over North America and Europe than the previous simulations suggested….”

18.  On 15 March 2011, a smaller cyclone over Japan developed rapidly and the radioactive plume from Fukushima was caught up in it.  The plume covered large parts of central-eastern Honshu and crossed over Tokyo and other major population centers before it left Japan towards the northeast around 18:00 UTC on 15 March.

19.  “…Between 16 and 19 March, an anticyclone passed from west to east over southern Japan…Westerly winds pushed the radioactive cloud out over the Pacific ocean…”

20.  ”’…However, on 19 March, winds veered from westerly back to easterly, pushing the cloud back to Japan.  Consequently, the plume penetrated inland, and covered large areas of eastern Japan…”

21.  “On 21 March, northeasterly windows transported the radioactive plume directly across Tokyo and even further south to Osaka, and Tokyo received an elevated Caesium 137 depositing on 21 March…”

22.  “…Consequently, Caesium 137 deposits in March was considerable for large parts of eastern Japan (Fig. 16, right panel)…”

23.  “…During the accident events, Xenon-133 and Caesium 137 were dispersed througout the Northern Hemisphere and eventually also reached the Southern Hemisphere…”

24.  “…The first radioactive cloud reached western North America on 15 March…containing Xenon 133…this cloud was detected at the Richland, WA monitoring station…”

25.  “…The heaviest concentration reached western North American 17-18 March.  This cloud was also heavy in Caesium 137.  At the same time, the plume pentrated the subtropics and arrived at Hawaii 19 March…”

26.  “… A map of the simulated surface concentrations of Xenon-133 (Fig. 18) for 22 March shows that all of western North America was engulfed by the Fukushima plume, as well as parts of eastern North America…”

27.  “…By 22 March 2011, the plume had covered the entire Northern Hemisphere and had reached both the tropics and polar regions…”

28.  “…We find that the Japanese main island received 5.0TBq of Caesium 137, or 19% of the total released, through 20 April…”

29.  “…Regarding Xenon-133, it is very likely that the accumulated inventory of Reactor Units 1 thru 3 was completely set free into the atmosphere between 11 and 15 March.  The study indicates a total release of 16.7 EBq, which is the largest release in history and 2.5 times higher than Chernobyl.

30.  “…Regarding Caesium 137, a total emission of 35.8 PBq, or about 42% of the total estimated Chernobyl emission was released…”

31.  “…Exactly during and following the period of the highest Caesium 137 emissions rates on 14/15 March, the plume was pushed towards Japan and affected large areas in the east of the island…”

32.  “…During a second episode from 20-22 March, even larger areas of Japan were covered, from Osaka in the south, Tokyo, and areas north of Fukushima…”

33.  A MAP showing the dispersion of Xenon 133 from Japan thru North America and the entire world, from 12 March thru 22 March: (click the picture to enlarge)

34.  A MAP showing the dispersion of Caesium 137 from Japan thru North America and the entire world, from 12 March thru 22 March: (click the picture to enlarge)

35.  A MAP showing the GROUND concentrations of XENON-133 on 22 March 2011: (click the picture to enlarge)

36.  A MAP showing the world wide total dispersion of Caseium 137 thru April 20 2011: (click the picture to enlarge)