A Guide to Book Collecting in the 21st Century: Information on beginning or sustaining a book collection (Alibris.com).
Bibliomania: For book collectors, or just book lovers, a vast collection of links covering topics from book repair to identifying first editions.
Book Terms Illustrated (powells.com): A helpful photograph accompanies each book term, along with its usage. Guide also outlines condition criteria.
Bookseller World: Bibliographies, articles and guides on book collecting and dealers.
Classic Crime Fiction: Highlights crime and mystery books, both from the reader's and collector's perspective.
Collecting Modern First Editions: Bookseller discusses collecting modern firsts (Alibris.com).
Collecting Telephone Books: The story of an uncommon hobby.
Exlibrisland.com - bookplates collecting and exchange: The ultimate source for exlibris collectors. Art of bookplate collecting. Bookplate magazine: history of ex-libris, bookplate today, ex-libris personalities - artists and owners.
FAQs: rec.collecting.books: Provides FAQs from the usenet newsgroup.
Guide to Rare and Old Book Values: Collectible book value guide, author autograph guide, eBay auction book selling tips, and book collecting links.
Information on Facsimile Books: An introduction to facsimile books, faithful recreations of the original.
The Bookplate Society: An international society of exlibris collectors, bibliophiles, artists, heralds, family historians and others dedicated to promoting the design, use and study of bookplates
Trussel: Books and Book Collecting: A large collection of information and links useful to book collectors.
Your Old Books: FAQs cover rare books and book values (not a pricing guide).