Eli Bendersky's website I just can't control myself - once in some time I get back to fiddle with Lisp. There's something about this language that feels so /right/ that I really want to get proficient at it, but it's hard, very hard.
Right now I'm going through some material from Norvig's PAIP, which is an excellent book. The example code (which is aplenty, showing nearly full, useful AI programs) follows Knuth's philosophy that "it's better to provide a non-trivial example that will take time to understand but will supply much knowledge, than a trivial example that doesn't add much to one's understanding."
The code is really advanced and takes time to grasp. But it's quite satisfying to understand it, and I feel that I'm learning.