A used book store chain in Texas (and presumably elsewhere). Their books are more often than not less than half price, especially for technical books. In my travels to the ones in Dallas and Austin the selection is pretty good, but like any other used-foo store, YMMV. Excellent place to buy fiction, as even hardbacks in good condition rarely sell for more than $5.

Forget dropping $7 on some crappy summer hype movie, spend it here and get a month's worth of amusement.