I spent the weekend reading The Code Book by Simon Singh. I found it incredibly interesting. It's a great overview of cryptography in general. But it also goes into enough detail that you can actually do the cryptography that he describes. Everything from the caesar shift to RSA and Diffie-Hellman-Merkle key exchange. I think that I might sit down one night here and code up a simple program that does RSA. At it's heart it's actually quite simple. Frighteningly so in fact.
So, I need another book to read. I'd like to keep on the track of crypto but another subject wouldn't be bad if it kept my brain working.