Another bot had a command I used to find very useful:
!steam
You'd use it to return the price and steam store page for a game; eg.
Nitebytes: !steam burnout paradise
icarusai: Burnout Paradise: The Ultimate Box (9.99 GBP)
http://store.steampowered.com/app/24740/I've had a search around the custom stuff and feature requests and couldn't see it, so I hope I'm not duplicating someone else's request.