Same as some of the other posts but also:

Don't overlook Amazon
http://www.amazon.com

In addition to new books they also have venders that sell harder to find new or used books.

Also, check out their sports and outdoors / camping and hiking section. Items vary, but sometimes they have some good deals. For example, today you can get a Victorinox Swiss Army Climber II Pocket Knife for $9.99 (free shipping on orders over $25).

Some are direct from Amazon, some from other vendors.