I sometimes come across posts asking about free curriculum usually its all online BUT if you are needing textbooks/workbooks etc. and aren't able to afford them there are a couple of places you can check into.
http://www.thebooksamaritan.com/ is one. You do have to contact them via snail mail to ask for the books and they will try and send you specific ones if you ask, but they are run on donations so you may not get exactly what you want, but you will get grade appropriate stuff. I've seen a couple of the boxes other homeschoolers have received and was impressed with how much they were given.
Another one is http://homeschoolcurriculumffs.blogspot.com/p/join-movement.html this one you do have to pay shipping and handling but the books are free. I have NOT seen any boxes from them at this point so I can't tell you much about them.
Hope the information helps someone, and if you can't use the information please pass it on to someone who can.