Read all about it: Books for the Road

Longitude Books: great place to start browsing
Goodreads: search for lists about places on the trip, culture, geology, etc. I made a list called "Travel XXXX" with the year and keep a repository of all the books I want to read for all the trips we're taking
Guardian UK Books: My favorite book section.
Um, Google.com e.g. "Books about Monument Valley"
Book Lust to Go: By Nancy Pearl. An oldie by goodie. My copy is well-thumbed for ideas about books I can read about places I want to go

Ann Patchett's Guide for Bookstore Lovers @ the New York Times

Another shout out for Indie Bookstores: Indie Bookstore Finder


I've dropped a mint at the following and would happily jump in my car right now to go to any of them:
Parnassus Books, Nashville TN
The Book Loft, Columbus OH
Gramercy Books, Bexley OH
Haslam's Book Store, St. Pete FL
Sherman's Book Store, Portland ME (and Camden ME): I know, it's a chain. But their fiction selection is AMAZING
Longfellow Books, Portland ME
Left Bank Books, Belfast ME: I'd probably own a vacation home in Maine if I hadn't spent so much at this store every time I go
Blue Hill Books, Blue Hill ME
The Country Bookseller, Wolfeboro, NH: Terrific fiction and really deep mystery section too