Although I'm all for supporting the school for various things, I can't help get my head around the price of textbooks. When I had to buy a fairly thin one for one of my classes, I was surprised to have to put down almost a hundred. To this end, and having learned how much I could save by doing some work, I must say that I:

1. Support buying books from other students.
I like to do this through the site comegetused which is owned and operated by a Berkeley alumnus and an UCLA student (and dedicated to promoting the exchange of textbooks among fellow students). My profile and books, should you want them are located here.

2. Use one of two sites, as they allow you to see a wide range of offerings and sometimes coupons that can be applied, ecampus and alibris.

3. A combination of buying books from the student store, buying the same books online for serious savings, receiving these books, then returning the student store ones. In this manner you always have the books you need, but are able to get the best price.

Slightly underhanded, but tis what you need to do sometimes :P