Hi, I'm Ryan. I figured I'd chime in while people are doing introductions.
Lisp games are an on/off hobby for me. I've got a decent amount of code on github: https://github.com/ryepup
I end up playing a lot with space ships, SDL, and bad AI. I like setting up a system and watching it go. I've been meandering towards to a tower defense game, starting with a simulation library inspired by Simpy (http://simpy.sourceforge.net/), at https://github.com/ryepup/rpd-simulation. To get this work I made a small coroutine library so I could have a "yield" statement like python, at https://github.com/ryepup/rpd-coroutines. There's some code at https://github.com/ryepup/rpd-simulation/tree/master/examples that shows these in use.
Eventually I'll put something together, but I'm firmly on the hobby end of the scale :)
Thanks, Ryan