Sure, Mac gaming is becoming less of an oxymoron these days, but if you want to game with a keyboard, Windows is still the way to go. Fortunately, Codeweavers' has concocted a solution for those who want the PC gaming experience on Mac (and Linux!) without using Boot Camp or partitioning drives. Introducing CrossOver Games.
We're not going to get into the technical side of it because, quite frankly, we don't understand it all. The Unofficial Apple Weblog (TUAW) has an extensive hands-on and gallery walkthrough (see below) of the $40 program, and found the software satisfying overall, especially for use with Steam. (You can view a compatibility list here.) There's also a 30-day free trial available.