I remember getting Scholastic Book club flyers as a child and poring over them for hours choosing exactly what to spend my allowance on. I remember turning in the paper form and the money to my teacher and I remember the joy of getting my little pile of books each month when they came in. It made me sad to think that my children wouldn't have that fun because our family is choosing to homeschool.
As it turns out, you can participate in Scholastic Book Clubs (now called Scholastic Reading Club) as a homeschool. You simply go to the Club Sign In Page and click on the "Don't have an account? Register now" button. Choose to register as an educator and then on the next popup page after entering your basic contact information you choose "Homeschool". You'll pick the grades you're teaching (you can choose more than one) and they'll send you paper flyers, but you can also do everything online.
Right now, if you make a $25 order, they'll send you a 10 pack of books with a teacher's guide for free (the book pack will correspond to the highest grade level you picked in your profile - if you want to receive a pack for a lower grade, simply temporarily remove the higher grades from your profile and add them back in later).
They have another amazing deal going on right now too. Teachers (including homeschool teachers) can purchase packs of 24 birthday coupons for $25. The coupons can be redeemed for books from any of the flyers for books up to a $5 value. So your $25 now can be redeemed for up to $120 in books during the rest of the school year.
I just made an order where I'll be getting 104 books for about 77 cents each (yes, I went a little crazy, but the deals are often best in the first flyer of the school year. The bonus points you are earning with the current order can actually be spent on the current order if you go into checkout and then back out again to make more changes. I used the points I earned on this order to "buy" additional books which is how I got the books down to 77 cents each. Well, that and I got a lot of multi-packs that were a good bargain.
I highly recommend the book clubs. It is difficult to find books elsewhere that match Scholastic's prices and they often have exclusive softcover versions of books that are only available in hardcover everywhere else. If you avoid the few ridiculously high prices items thrown into each flyer you can easily get 7-15 books a month for about $1-$1.50 each. You can also skip a month whenever you like.
If you happen to be in a homeschool organization one person can sign up as an educator and then distribute flyers to everyone else. The other parents can sign up for parent (rather than educator) accounts and use a code given to them by the coordinator to place their orders and pay for them online.