It is essential that one read the FAQ or description on each link, to know what is being monitored,
how often it is updated, etc.
This link has measuring sites across the country , thus the entire USA map is displayed.
Measurements are taken by volunteers who report the numbers.
I note there are more sites now than there were a few weeks ago.
http://www.radiationnetwork.com/This link is a stationary monitor in LA area, you have to click on a link for the FAQ page.
http://www.enviroreporter.com/2011/03/enviroreporter-coms-radiation-station/This is a map of world, you can play loop of 3 different kinds of radiation over 3 places on the planet,
over time, per type of radiation. http://www.woweather.com/weather/news/fukushima?LANG=us&VAR=niluhemis131&HH=0This is the EPA page of chart(s) depending on what you click on:
http://www.epa.gov/radiation/rert/radnet-seattle-bg.htmlLastly, this is a Seattle area update of air quality, again, you have to poke around to find what you are interested in:
http://www.doh.wa.gov/topics/japan/monitor.htmPlease kick if this is helpful, I have bookmarked for updates.