Maggs Bros. 
www.maggs.com
Take a stroll through this cozy Brit site’s virtual antiquarian store. Devoted staffers have built up a collection of  thousands of books, ranging from military to travel to autographs to natural history. Among their recent prize offerings was an illustrated miniature of St. Adrian—circa 1470—taken from a Book of Hours. For those just getting started as book collectors, there are tomes on said art and an excerpt from Portrait of an Obsession, about bibliomaniac extraordinaire Thomas Phillipps. The 151-year-old store on Berkeley Square in London remains as solidly British as ever; even on the website, Maggs quotes its prices in pounds.

Antiquarian Booksellers Association of America
www.abaa.org
This jam-packed site offers many tools through its primer on rare book collecting, and is essential reading for neophytes. The concise glossary defines terms like folio (books more than 13 inches tall) or broadside (single leaves of paper printed on both sides). Seasoned collectors can search for a book by publishing date or edition, or they can locate an association bookseller, as well as surf through news about upcoming book fairs.