ABAA: Antiquarian Booksellers' Association of America, the national association of antiquarian dealers.

ILAB: the International League of Antiquarian Booksellers, an international organization of dealers.

MARIAB: Massachusetts and Rhode Island Antiquarian Booksellers, a regional association.

ABA: American Booksellers Association, the national association of new-book dealers.

LOC: The Library of Congress Web Pages, which continue to expand daily

There are a number of other sites of interest to the book researcher:

The American Library Association maintains a comprehensive Web site with information on their organization

Conservation OnLine accesses to resources relating to the preservation of books and manuscripts, located at Stanford University

Z39.50 Web Interfaces are a new approach to library research using Web forms. Try the Library of Congress Web Gateway.