[timestretch]

http://projecteuler.net/ is fun. You write programs that yield an specific answer. Paste the answer in to find out if your solution is correct. I clicked around and worked on the questions that seemed the most interesting.

In terms of books, TAOCP may be a bit more general than what I was thinking of. I assumed you were getting back into programming to make something specific. What sort of software do you plan on working on? Answering that question first may help you spend your coding time more effectively.