Other World Computing for Mac stuff. Depending on the MacBook you have, a hard drive installation is a breeze. You could probably get by with the 13.3" MacBook instead of the more expensive 15.4" model. Just get a video adapter and run a second monitor for the Adobe CS apps. Oh yeah, max out the RAM. That will help with Photoshop, InDesign, etc.
If you're just doing email, web, and simple docs, a netbook looks like the best option. Some will even run Leopard. BoingBoing has a great chart with info on what works. The Dell Mini 9 and Lenovo S10 look to be the best bets to run OSX.