I really enjoy reading Crystal's blog (I am pretty tired and have forgotten how to post a link in my post, but her link is in my sidebar) and she has a Frugal Friday's tip day!
My tip is about homeschooling cheaply. When it comes close to school time, I look around my house for schoolbooks that from the year before I have not used or that people have given me. I have found that when you homeschool often people will give you books that they do not need anymore. You can use them or what I do if I cannot use them, is sell them and use the money for the schoolbooks I needed. Most of the ones I get were from garage sales, second hand stores or give aways. I sold a few textbooks I picked up at the library at $1 each on half.com and got enough money to buy the rest of the school books I needed. Next year I will sell the non-consumables we will not need again and buy new things.
Other things I do is borrow schoolbooks, like expensive teacher's manual's or buy used.