Codeweavers tells us that they've released version 8 of their Crossover Games software -- I tried it out a while ago, and found that while it was a pretty good way to play their recommended games, once you went off the reservation, things got a little hairy. Then again, that was a long time ago, and since then, they've updated the recommended games list quite a bit -- they're now saying that version 8 will allow you to play most of the Steam games, including the excellent Left 4 Dead, and the new Tales of Monkey Island episodic games.
Additionally (and perhaps we're burying the lead a little bit here), this version is completely compatible with Snow Leopard. So while you still may be banging your head against compatibility for some apps (I'm actually sort of glad now that SL was sold out at Best Buy when I went by to pick it up -- think I might just wait until the compatibility issues get ironed out), Crossover Games should work just fine.
And it of course works on both Mac and Linux, so if you have a spare 'nix box sitting around and want some Windows games running on it, there you go. Existing customers with a support entitlement can upgrade right away, the app can be bought for $40, or there's a free trial to try out as well if you'd rather do that.