I've built a couple for grins of the redhat, hostap, nocat variety. However, you can pick up an 802.11b AP for $30 bucks, so I would say that it really isn't worth it for just for surfing.
If you want it just to play with and use it as a learning environment, then its worth it. You might also want to try a live distro first, such as:
http://www.lessnetworks.com/static/download.html