So, I found an interesting link via Google about an hour ago.

http://forums.steampowered.com/forum....php?t=2544489

It's a thread on the Steam forums that keeps track of currently running "indie bundles", ie. bundle sales outside of Steam that contain Steam keys.

Highlights at the moment:
One bundle containing the Gundemonium collection and Serious Sam 2, if you're into FPS or shmups
One bundle containing Avernum 4/5/6, Oddworld 1/2, Postal 2, and a couple of other games
A couple bundles containing games that I wasn't particularly interested in