Toothpaste and peroxide? A simple GOOGLE search turns up lots of info on how to make a dirty bomb but fear not:
http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/dirty-bombs.html

What they fail to mention is that after your shower you need to make an emergency trip to the grocery store and stock up on whatever you is still left on the shelves. You won't be seeing food or water for a while.
After Spetember 11th we all held our breath and waited for the news that the attack had been nuclear. Osama missed a real opportunity there.