Chat with megahal an teach him new words and sentences. 
I originally started to play arround with it after I read a hillarious article about somebody combining Eliza with AOL instant messenger. So I created my own toy by combining Megahal and ICQ instant messenger.
This is now ages ago and all chat logs were pitfully lost. But I learned a lot about IPC using Perl.
Later I created this as a widget on my web page and learned again about shipping data through a lot of different stuff (CGI, TCP, whatnot).
The fourth and current generation is now served through a single stash of Perl scripts not only wrapping the megahal executable (which always has been a black box to my creations) but also serving the needen web content. This time I learned not much. I basically created this version because Megahal in the meantime has been used in some art installations.
If you like this stuff, you can email me and I’ll send you everything you need to run your own.