I just finished leafing through Schneier's "Applied Cryptography", second edition. Lots of new stuff, good and very thorough coverage of protocols and implementations, including weaknesses and processes behind same. If an idiot like me can understand this stuff (and if you don't believe I'm an idiot, just ask Perry), anyone can. I highly recommend the book, it's an absolute bargain at $50 USD. Should be required reading for anyone before being allowed to post here. :)