A recent challenge amongst chatterboxes: http://www.chatterboxchallenge.com/
Here is some info on some of the bots. Could be used as a fun activity to look at AI.
1. Here’s a downloadable chatterbox called Artemis : http://users.auth.gr/~dkaras/
2.Another one called RoboMatic X1 looks really interesting! http://www.infradrive.com/robomatic.php
3. A Web-based chatterbox, Azureon: http://www.personalityforge.com/dynachat.php?BotID=23969&MID=23957
Here is another list of bots: http://www.personalityforge.com/botlist.php