The best source of data and analysis I've seen is the Physics Forum thread on Japan Earthquake: nuclear plants. This has commentary from radiologists, nuclear engineers, former nuclear power plant operators, physicists, and in general, a lot of people who know their stuff. It's confined to the physics of the situation.
A more politically-oriented thread on the same forum is the aptly named The "more political thread" besides "Japan Earthquake: nuclear plants" scientific one
Now some of the hard data regarding the power plants. First, the general environmental radiation close to the reactors, and a few hundred metres away. Note that Your Radiation May Vary, with hot-spots considerably in excess of these figures just metres away.
Now a bit of a worry: the aftershocks continue, so in addition to there being a generally high level of atmospheric and "skyshine" radiation from scattered gamma rays, plus the "hot" water that's at 100 Rem/Hour in places, plus the internal environment adjacent to the reactors which may be more like 2,500 Rem/Hr (down from 10,000)... the buildings are F*cked, to put it bluntly.
The toughest components were designed to take 440 gals - that is, sideways accelerations of up to 440 cm/sec/sec. They took 500.
Then got hit by a tsunami that inundated the buildings up to about 3m, from the looks of it. The traditional overturned semi-trailers, displaced cars etc.
Then took 3 separate explosions, one of which was considerably more violent than the other two, and partly directed sideways. The whole plant, all the buildings, are a mess, airtight they're not. Watertight they're not either, there's cracks everywhere, foundations, pipe channels, electrical conduit ducts, and the "hot" water will get everywhere eventually. Time is not on our side here, the contamination is getting worse and worse just as the reactors themselves are in dynamic equilibrium, being adequately cooled by water injection rather than circulation.
But it's worse than that, because aftershocks are still hitting the region, major earthquakes in their own right. If the buildings were structurally sound, no great drama, they could take that easily. But they're damaged, sometimes severely. Band-aid patches to stop water flow aren't supposed to take such treatment, even if they do work initially.
Note that in the following diagram, the severity uses the Japanese measure. Add about 12% to get the equivalent Richter magnitude.
Source: Graphing Earthquake, Radiation and Water Data in Japan
A technical challenge... and getting just a bit more difficult with every hour that passes, just as the environmental radiation some distance from the plant is becoming less hazardous. The most complete and accurate readings of the general area come from the extensive radiation monitoring equipment at the nearby Dai-Ni Nuclear Plant.
Compare and contrast to the Dai-Ichi figures.
And just to make your day... pressure in #1 Pressure vessel is rising (good that it's not leaking - the others are at ambient pressure), and so is radiation in the drywell surrounding it. Now close to 5,000 Rem/hr, and 650 kPa pressure, 250 over the usual (4 atmospheres - 400 kPa). Oopsie.
Source : http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/plot-un1-full.png based on #Fukushima reactor temp, pressure, water level+rate, CAMS radiation to #NISA / #METI release 72 (apr/04 08:00).
More Details on individual reactor status at Japan Atomic Industrial Forum Information on Status of Nuclear Power Plants in Fukushima
This is going to need a decade-long cleanup.