Great ideas, everyone!
CupcakeGuru, I'm going to check out thriftbooks. Iris lily, my Goodwill charges $1-2 a book. I will only pay that much for a specific title we're looking for. How much does your Goodwill charge? At the Goodwill Outlet near my parents, children's books go for 50 cents.
SimplyMarvie, I will try your moving trick. We already have gooki's book wish list down. There are some books, like the giant Richard Scarry ones, that I know will get so much use that they need to be bought new and those ones go onto the wish list for birthdays/holidays. frugalparagon, I wish that my library gave away books for free!