Common Lisp also happens to be an excellent language for AI.
The CMU Artificial Intelligence Repository contains a wealth of both Lisp and AI (as well as Scheme and Prolog) related documents and code.
The Artificial Intelligence Algorithms Wiki was a new AI resource, but it is currently offline. The Artificial Intelligence Wiki may still be available.
If you use GNU/Linux (and perhaps even if you don't), see also the GNU/Linux AI & Alife HOWTO
Theorem Provers, previously listed under AI, have been moved to their own subtopic. Other subtopics include Knowledge Representation Systems, Natural Language Processing, Distributed AI...
AI Books
- Books on Artificial Intelligence and Mathematics, with a Lisp language emphasis from the ALU website
- Building Problem Solvers describes how to build reasoning systems, using Common Lisp source code available at this web site. The code includes a variety of rule engines, truth maintenance systems, and constraint systems.