At the used book fair we went to a couple of weeks ago there was a CHEC booth with several tables full of books for only fifty cents a piece. They were books that had been donated that CHEC doesn't have room to store.
I picked up several books on homeschooling. My favorite so far has been "A Patchwork of Days" that gives a day in the life of many different homeschooling families. Another book I found has a bunch of literacy games in it and instructions for how to make them into "literacy folders" like these. The instructions for the game are on the back of the folder and the pieces are inside. There's also a sheet to write your answers on. When Danya and Gloria need a fun break (or if the phone rings or some other temporary interruption comes up) I let them work on a folder. They really enjoy them. My favorite so far has been the one on homonyms.