James Wesley, Rawles has linked tonight to a useful web site relating to radiation levels in the US and Canada. If we do start to see radiation drift over here from the events in Japan this might be a very useful site to check out frequently. The link is here: http://www.radiationnetwork.com/RadiationNetwork.htm
Also of possible use is the following map of the Northern Pacific jet stream: http://www.stormsurfing.com/cgi/display_alt.cgi?a=npac_250
Hopefully none of this will be needed, but it never hurts to be prepared.