Keep on the lookout for children's books with great artwork at your local thrift shop and garage sales. Worn or damaged make no difference when you're cutting them up. In fact, yay you for saving a book that probably wouldn't get purchased otherwise!
This would work well with old cookbooks for a little kitchen art, especially books from the fifties to seventies. Is it just me, or did the 70's have a major love for the hotdog as a main ingredient in everything?