online booksellers

amazon.com
barnes and noble
borders
booksense.com
powells books
half.com
edward r hamilton

travel bookstores

travel books now
travelknowledge
globe corner bookstore
magellan travel books
longitude books
travel guide warehouse

adventurous traveler
distant lands
the travel bookshop UK
wide world books and maps

Picture/Coffee table books

Sometimes, you buy books for their pictures, not their content -- and I found both of these books on the remaindered pile at Borders, they were a cheap addition to the growing pile of books next to my couch.

When the Pyramids Were Built
Egypt: World of the Pharaohs

There are dozens more, of course. And, if you aren't as dedicated a collector as I am, the library has shelves full of the things to browse through.

You might, of course, be more interested in the actual history and reference books.