on the subject of GMA500.. don't let it totally dissuade you away from, say, the Fujitsu U820 (aka U2010). It's a great machine, and you can get linux working on it pretty well with accelerate video, it's not too hard but it isn't trivial.

there's now a pre-prepared ubuntu with the drivers installed up-front, so that's a real step forward
http://forum.pocketables.net/showthread.php?t=6192

I am very happy with my U2010, I don't know what I'd replace it with if it broke, there's nothing quite like it around, it really does do the job of a handheld linux laptop.