I just finished Star Wars: The Force Unleashed on Sith Warrior on the Dark Side. I heard the Darth Maul fight and Star Destroyer level were pretty tough, but I got through them easily. The second Vader fight kinda pissed me off though. I plan on playing through it again on Sith Master to try to get all the holocrons and the rest of the achievements.
I've also been working on getting all the achievements for Forza Motorsport 3, so as a side project, I've been going through the event list. I'm about three achievements away from having all of them.
Next up, I can't decide between Dante's Inferno, Gears of War, or The Force Unleashed II. I'm definitely picking up Assassin's Creed: Brotherhood in the next week, so the next game I play will be filler between now and then.