And here's a site to help you mark your location and potential damage regarding a nuclear blast. I know there's another one, but I haven't found it yet:
Thank you Dearheart, you have mail
Feds Concerned U.S. Terror Attack in Works
http://www.foxnews.com/story/0,2933,133281,00.html
Nuclear Blast Damage
http://www.pbs.org/wgbh/amex/bomb/sfeature/mapablast.html
Thanks for those references.