Mac OS X Netbook Compatibility Chart (Updated July 2009) Update: This has been useful for many people, which is very rewarding, but I don’t have time to maintain it anymore.
Sorry! Instead, a straightforward answer: Get a Dell Mini 10v and use this guide to put Snow Leopard on it. Apple says it’s had “pretty interesting ideas” for a Mac netbook, but it’s everyday users who’ve already taken action. Most of the popular netbooks can run OS X, but there are plenty of caveats: non-functioning components which lack drivers, need to be replaced, or which simply can’t be gotten working at all. The State of Hackintosh: Which Netbooks to Hack - Mac os x netbook chart - Gizmodo.
How To: Hackintosh a Dell Mini 10v Into the Ultimate Snow Leopard Netbook - Dell mini 10v hackintosh - Gizmodo.