Froogle:
Developed by Google, Inc. One of the most promising price comparison sites to date.
BizRate:
One of the largest price search sites. Over 30 million products listed.
Shopping.com:
Child of Dealtime and Epinions, now merged to provide you with three shopping search engines that feature your products separately, yet the same.
Yahoo Shopping:
Complete Yahoo Shopping data feed creation and maintenance solutions.
MSN Shopping:
Complete MSN Shopping data feed creation and maintenance solutions.
NexTag Shopping:
Complete NexTag data feed creation and maintenance solutions.
PriceGrabber Shopping:
Complete PriceGrabber data feed creation and maintenance solutions.
One Book Worm
Rare, out-of-print, and secondhand books.
Over-Sands Books.
Varied stock of antiquarian, second-hand, and out-of-print books for sale. The Shop is situated at Grange-over-Sands, UK.
O and I Books
Second-hand bookstore. Specializing in English and Spanish rare, hard to find antique 1876-1997 books.
On the Shelf
Buys, sells and trade used books in all genres. Includes comic books, collectibles, series and first editions.
OldBookShop.Com
Used, out of print, and rare hardback books.
Olof Edlund
Antiquarian and rare books and manuscripts in all fields.
Old Paper World
Rare books, magazines, newspapers, ephemera; a broad cross section of rarities in many fields.
Olde South Books
Used and rare books, including medical, genealogy, fiction, biography, and religion.
Observer's Swap Shop
Swap site for Observer's Pocket Series books published by Frederik Warne from 1937 to 1982. Membership required for full service.
Owl at the Bridge
Scholarly, rare and unusual out-of-print books. Primary interests are Italian history and culture and American industrial silver.