Book Related Sites
International League of Antiquarian Booksellers (ILAB/LILA).
Book History Online. Searchable database of bibliographical reference sources.
RPS - Tremendous listing of over 5000 websites describing holdings of manuscripts, archives, rare books, historical photographs, and other primary sources...
The British Library - Amazing collection of Virtual Books displayed with turning Pages technology.
Cotsen Children's Library - Perhaps the greatest collection of Children's Illustrated Books ever assembled.