"Book Burro - Remixing the bookstore" was such a helpful script, but it has not been working for a while. They do have FireFox BookBurro Addon, but it is really not that thorough and very hard to modify. So here is new and improved working GreaseMonkey Script: http://userscripts.org/scripts/show/65482
Fixed, New Features, Improved:
Fixed: All price are now properly extracted. (extraction starts as soon as you are on book page so you do not have to wait)
Included new reliable sources for books: Ebay.com, Walmart.com, Craigslist.com, Strandbooks.com, Betterworldbooks.com, Ebooks.com and Kindle Editions.
Removed all useless sites like: ecampus.com, bookbyte.com, bookpool.com, biggerbooks.com, buy.com, Do Not Buy (a1books).com, booksamillion.com, biggerbooks.com
Following sites are now being searched: