The Personality Forge - a great place to build bots, chat to bots, chat about bots, and hang out generally. Don't feed the dragons (oh alright, you can feed Bildgesmythe - he's a nice dragon,) and watch out for Glindar (a problem personality with an unhealthy fascination with knives!)

The Book of AI - the Personality Forge's 'Bible'.
How to build bots, from the basics to advanced techniques. Read it, re-read it. Then read it again. Print it out and reread it until you know it backwards.

ALLY - a standalone bot designed by Colonel720
I can't get Ally to work myself, but if you can, you'll probably like her.

Nick - another learning bot designed by Colonel720, and he ROCKS! Seriously, this is certainly the most impressive learning bot I've seen yet. He uses an artificial neural network to analyse and learn language, can handle speech recognition and synthesis, and can use a webcam to "see" and learn about the world outside the computer. Plus he can be taught by letting him read text files or webpages.
Download him immediately - you won't regret it!

NEW! Transcripts and observations from my own experimentation with Nick.

Heimdall's website - Heimdall is a virtual Norse God (but he doesn't speak Old Norse )

Poseidon - The Sea-God himself!

The Chatterbox Challenge - a contest for chatbots
The 'Oscars' of the AI World

Billy and Daisy - The classic learning bots by Greg Leedberg.

To be continued...