If you're searching for book values - try these links:
American Library Association
International Book Collectors Association

Automatically compare prices among major, reputable online bookstores and finds the internet-wide best offer for almost any book you want.
Add All.com
http://www.addall.com/

MEMBERS LIST	CITY DIRECTORY	BOOK SEARCH	BOOK FAIR	SPECIALTIES	SERVICES
ANNOUNCEMENTS	MEMBERS ONLY