Where Can I Buy Used Books?

amazon.com is a great place to check

Try Craigslist. I have seen some listings for kids books, like a box of book for $10. Also, some Goodwill stores have books that are not beat up. If you are near a Catholic school, ask if they have book sales during the year. My kids used to go to one and they had a book sale every year to raise money for new books. Many people still have garage sales also. I live in Berwyn and the local Life newspaper has listing under Bargain sales. check out www.mysuburbanlife.com Forest Park/Berwyn/Cicero all have the same listings. You can sometimes find bargains there. Unfortunately there aren't many used book stores around the area with good kids books.

Goodwill and Thrift stores!!

I think half price books (google for the closest location) has kids books! You can also take your old books in and they will buy them from you!
It's addicting if you are a reader or LOVE books cause the prices are so incredibly reasonable.
There's also Freecycle.org. You find your community and either wait for someone to post free children's books or post a wanted for them. It's a great way to recycle and one persons garbage is anothers treasure! I encourage everyone to sign up especially with our economy! I have been blessed and have in turn blessed others through it, and saved so much money!
Hope these help.