Here are some useful links if you're looking to buy, sell, or find out information on, textbooks.

Local bookstores | Buy textbooks online | Sell textbooks online | Buy/sell books locally | Get information on books

Local bookstores

University of Waterloo Book Store
Laurier Bookstore
Feds Used Books
Words Worth Books

Buy textbooks online Textbooks

Sell textbooks online

bookmob buyback
Buys back a wide range of books.
AbeBooks buyback
Worth checking prices offered here. Minimum $50 buyback.

Buy/sell books locally—University of Waterloo—WLU
Books2go—University of Waterloo
Books2go—Wilfrid Laurier University
Kijiji Kitchener/Waterloo

Get information on books

Google Books
A large catalogue of books.
Open Library
This site also uses some of their cover images and APIs.
The web's largest community of book lovers.