The Asus EePCs are pretty decent and inexpensive. Keep in mind that he won't be able to do much on a netbook, aside from surf the web. If he's into any kind of gaming or anything that's going to take a lot of space or RAM, you might want to consider a regular pc or mac.
But, if you know you want a netbook, keep your eye on Dealnews.com- there are some great bargains on the for netbooks. We've been considering one for my daughter, who is just learning to use a mouse and thinks the most exciting thing in the world is starfall.com, and we've been watching Dealnews for one for her Christmas present.