The great thing about the wall method (which I am sold on, btw) is that it is not only cheap, but infinitely expandable (until you get to the end of the wall).

One simply purchases boards (I used pine, but you can use maple or oak if you want to be fancy) and attach the runners on the inside. Using brackets you attach the big board to the wall and then simply fit the shelves in.

All of the lumber is pre-cut at Home Depot, but if you need it cut a certain length, the guys there will do it for you (they didn't even charge me!).

It's idiot-proof; you don't even have to know how to hammer a nail straight! I used screws.