Netbook (MSI Wind, Mini 9, EEE, S10) Mac OS X compatibility chart
The Macbook Air is a nice bit of kit but it's expensive and mucho oversized compared to the netbooks out on the market (yes of course it is also more powerful). If you have a hankering for Jobs to release a real super-light laptop, but don't have the patience to wait several years, you may want to consider creating a hackintosh by installing OS X on an existing netbook.
Here is a compatibility chart from BoingBoing Gadgets that shows the current possibilities. Surprisingly Dell is the most compatible with the Mini 9 running perfectly under OS X.