Here is what is left of the list I had. Some of the original sites had disappeared and others have been swallowed by Barnes&Noble (or in one case by a pornography site!). The first one lists and compares prices at other sites.

• theuzone.com (textbooks.studentmarket.com/) (www.studentmarket.com/textbooks.html)
• ecampus.com (this site has a horribly slow load time due to a slow background that apperently has to be generated even though it is almost entirely covered by other things once they load...Bad Design!! But they claim to have new and used copies available for immediate shipment.)
• bigwords.com
• efollett.com
• varsitybooks.com
• www.wizeup.com