Blatant Plug: For people who are irritated with amazon.com, I’d recommend Powell’s Books.

They have a very usable site (unlike all of Amazon’s competitors, which I tried and gave up on), and are an actual Brick and Mortar store for those of you concerned about e-commerce wiping out conventional stores. Plus, they carry used and out-of-print books and offer free shipping if your order is over $50. I’m not affiliated with them in any way, I’ve just been really happy with their service and their tendency to not be bastards.