Another site that I missed mentioning this blog recently is the excellent dataisnature.
I didn’t realise that the author of dataisnature was one of the contributors to Flash Math Creativity, now in a second edition updated to use the new Flash ActionScript syntax. I found the first edition an inspiration, the sort of thing I wish I’d had when I was learning to program art (and teaching others to program art).
Each chapter features a series of simple but engaging algorithmic art projects, beautifully illustrated, with full code and explanations. It’s directed at Flash users, but if you can understand JavaScript it’s easy to transfer the ideas to Processing, which is probably better for pure generative work.