Apple has yet to enter the Netbook space, no doubt they have something in the works but users not content to wait have taken things into their own hands. Depending on what Netbook you have you may have to sacrifice some functionality but overall some like the HP Mini 1000 or a Dell Mini 9/Vostro A90 are quite comprehensive in their support of OSX.

Installing on non Mac hardware likely infringes Apple’s end user license agreement so don’t expect any official support. Check out this compatibility chart to see what your Netbook can do.

Dell Mini 9 installation guide by Gizmodo

MSI Wind installation guide by Wired

HP Mini 1000 installation guide by myHPmini

Asus Eee PC by uneasysilence.com

If you run into any problems you can get support over at the Hackintosh forums.