The No 3 reactor at the Fukushima power plant just had a hydrogen explosion like the No 1 reactor did on Saturday.
So far, it looks like the reactors can be shut down and may have experienced a partial meltdown of the core (like a 3 Mile Island situation). It doesnt look like there will be a Chernobyl type situation as No 1 and No 3 were in the worse condition. Pumping in the sea water has worked to keep the core covered, but wasnt exactly how they wanted to do it as these reactors will likely never function again.
I don't think Japan will be a nuclear crater, but I am concerned about the infrastructure after this stuff all calms down. If they lose many more reactors these power shortages may become way more common place for about a year or more.