Cardinal Quest is a commercial roguelike by indie developer Ido Yehieli. For one day only he's giving his game away for free:

http://twitter.com/#!/tametick/statu...85642504372226

I reviewed the game recently on the Roguelike Radio podcast. It's a fun dungeon crawler, with retro graphics and music, and a big emphasis on interface polish. Nowhere near as deep as ADOM, but it sure teaches some lessons on how to make a game easy to play.