Here are some sources for news and analysis on the nuclear events in Japan to consider:
Areva’s analysis as of April 1
Wikipedia’s entry for the Daiichi nuclear crisis
Germany’s Federal Ministry of the Environment, Nature Conservation and Nuclear Safety BMU (site includes spent fuel bay inventory and thermal power estimates)
Japan’s Ministry of Education, Culture, Sports, Science&Technology publishes radiation data here.
The New York Times maintains an updated chronology of major developments here.