Obama went on record today, definitively stating that NO harmful radiation is going to float over any of the 50 states, and that his experts DO NOT recommend any preparations other than listen to his hot air.
President Obama on Japan Nuclear Crisis: No Harmful Radiation in U.S.
Other sources
NY Times: Minor health problems possible in North America
USAToday: U.S. radiation experts try to decipher reports from Japan, Impossible to gauge danger
Interactive Forecast map for path of Radioactive Plume - NYTimes.com
President Obama on Japan Nuclear Crisis: No Harmful Radiation in U.S.
"I want to be very clear: We do not expect harmful levels of radiation to reach the U.S., whether it's the west coast, Hawaii, Alaska, or the U.S. territories in the Pacific."
"The Centers for Disease Control and Prevention and public health experts do not recommend people in the U.S. take precautionary measures beyond staying informed."
"The Centers for Disease Control and Prevention and public health experts do not recommend people in the U.S. take precautionary measures beyond staying informed."
Other sources
NY Times: Minor health problems possible in North America
USAToday: U.S. radiation experts try to decipher reports from Japan, Impossible to gauge danger
Interactive Forecast map for path of Radioactive Plume - NYTimes.com