All About Learning – they have a money back guarantee on their products *Many products are special needs friendly
Rainbow Resource Center – some items may be aligned with Common Core, but products aligned to Common Core usually say so.
The Book Samaritan -“The Book Samaritan is a non profit organization that supplies homeschool materials to families the are unable to afford them. We send curriculum and supplies, free of charge, to homeschooling families in need. We could not do this without the help of people who are willing to donate their curriculum and books. Our ministry relies on you. From the bottom of our hearts, we thank you for your generosity.”
Amazon is a great place to do comparative shopping and used books are a great way to save money.