When I first started scoping the NET for used books I found that they were EVERY where !!! So I have put together some of the Best sites to check out!!

Ky-on-line Used Book Board The BackPack
Peabody's Mom's Homeschool Attic All Used Curriculum Board
Sipes Family Homeschool Page Great Used Books for Families Book Shelf
Homeschool Store.com Chris' Book Basket Heather's Homeschool Hideout
vegsource Homeschool swap boards Randi's Reruns Homeschool Resources Carty's Curriculum Corner
Newlife's Place of Homeschooling Books CTR Academy Bookstore Used Homeschool Stuff and More!
Blanc's Used Books Used Home School Books Christian curriculium Cellar
Bookheads California Swap Board The Book Mobile On-Line