I buy from Amazon all. the. time. A friend just passed along this deal to me, which is good only for the next 20 hours.
$20 Amazon gift card for $10
For full disclosure, if three people buy through the above link, I'll get a free deal in the future. You can also go to www.livingsocial.com. Regardless, I just wanted to share this deal since I know many homeschoolers love Amazon as much as I do! Off to buy some books!