- Dragon Age Origins (Mac) is excellent!
I purchased DAO from Direct2Drive for $49.99 (I believe it's a 9gb download, keep in mind D2D does not have a download manager for OS X, so you'll need to use something like iGetter to download all of it since Safari and most browsers will not download a file over 4gb, though I think FireFox can-- it has at times not resumed stalled downloads.) There was a 50% sale recently on all Mac games at D2D (grumble); I was able to get X3: Terran Conflict for $19.99 during that sale, great game though a steep learning curve.
Some other noteworthy games at D2D:
- Shaun White Snowboarding
- Command & Conquer 3
- Flatout 2
- Puzzle Quest
The sites I use to look for Mac games are:
- Direct2Drive
- MacGamesStore
- (Steam for Mac) When it comes out.

- Aspyr: They apparently have a "gameagent" for mac coming soon, and I just noticed they have Star Wars: The Force Unleashed for the Mac, as well as many other noteworthy titles such as Call of Duty 4: Modern Warfare, and Star Wars: Knights of the Old Republic.
On the MMO front- Fallen Earth (a post-apocalyptic MMORPG) now has a Mac Beta Client, it runs alright on an MBP, though much better on my iMac. The rest of the games I play are under bootcamp Windows.
TIP: I found that Dragon Age Origins (Mac) runs much smoother in windowed mode, in "configure" select a resolution just under your native one (i.e. 1280x800 if your running in 1400x900); while in-game press cmd+enter to go into windowed mode.
I just recently picked up the higher-end of the 21.5" iMac's, and Dragon Age Origins runs impressively smooth on medium to high details. It will run in 1920x1080 alright, but best to use something like 1280x720 or 1366x768.