We just started searching BiblioDirect, a new American listings service for used and out of print books. It's a nice looking site, and they seem to have gone to a lot of trouble to make sure that they have clean, well-fielded, book descriptions.
BiblioDirect is run by Lynn DeWeese-Parkinson, the Grand Poobah of the Bibliophile mailing list. The Biblio list has long been considered the most important list out there for folks working in the online used book industry.
Posted by Anirvan