I'm all over the place right now.
Bioshock - Farmer's Market.
Contra 4 - Boss of level 4.
Brain Age 2 - Just started, though it's not really something you can "complete."
Team Fortress 2 - Can't really say where you are, since it's MP only, but I figured I'd at least list it.
Puzzle Quest - just took out Dugog.
Mario Galaxy - just unlocked the second galaxy.
I think that's it for now. So many new games last December, I have a feeling there will be a lot that I quit before I finish, particularly since there are a number of cheap adventure games (mentioned in another thread) that are calling my name right now...