Because of your choice to get the MacBook (eew... GMA950 video card, don't worry I have one too)... you are really limited in gaming. and you have more options then I've seen mentioned. On my macbook if I play games, it's either on console emulators, DOS emulator or a OS X native game (there are more then you think). I hate using bootcamp, as I don't like rebooting every time... and again because you don't have a macbook pro (which has a good 3d video card, geforce 8600 currently), fully booting in to windows isn't really worth the time. Here is my list of gaming options on Mac.
1) Mac OS X Native games... just go through the category search on pirate bay or mininova, you'll find more then you think. (including lots of unofficial ports using Cider;
http://www.transgaming.com/products/cider/)
2) Playing Windows games via Virtual Machine or WINE... via parallels or vmware is ok, if not's not too graphically intense (but can't really be graphically intense due to your macbook's video card)... or there is now crossover games (http://www.codeweavers.com/compatibility/browse/group/?app_parent=4100) that could do this too.
3) Playing DOS games... this one is my personal favorite... love the retro DOS games (easy to find abandonware downloads for these games), and DOSbox is awesome for this. (http://www.dosbox.com/)
4) Old console emulators... there are very good emulators of Genesis and SNES available on Mac... another great way to get your gaming fix on the Mac.
One of the things I did before going to Mac... understanding that my "real" gaming on a PC is over with... but that's 100% fine with me since I have my 360, Wii & DS to play games on... but when my MacBook is the only option with me, then at least I do have a few options more then Solitaire (i do love my solitaire widget though).