Thriftbooks.com yet? If not, you should check it out!
This is a wonderful website with thousands of great used books. There are many, many books priced at $3.95 (US Dollars) and, the best part--FREE SHIPPING! That's right--FREE SHIPPING! It doesn't get much better than that. I have placed three orders through Thriftbooks and have been very satisfied. It took about a week (maybe a little more or less depending on where you live) to receive my order. The books arrived in the condition which were specified. If you haven't checked out this site, there is no reason why you shouldn't.
If you have ordered from Thriftbooks before, please comment on this post and let us know your experience!