Bookfinder.com compiles textbook prices from many different sellers, and returns the info sorted by author. Once the desired author is selected, options are returned in order of cheapest to most expensive.
In addition to the North American version of AbeBooks (AbeBooks.com), there are localized version of AbeBooks for UK (AbeBooks.co.uk), Germany, (AbeBooks.de) France (AbeBooks.fr), Italy (AbeBooks.it) and Spain (IberLibro.com).
Many users have complained about information inconsistencies, shipping problems, and wrongful refusal of refunds. The percentage of orders that are actually fulfilled is estimated to be about 20%. While this isn't always the fault of AbeBooks.com, it might just be a lack of proper oversight.