I'd say 1/3 of the curriculum we work on at homeschool has been books and materials that have come to us freely. Whether friends/family pass things along that they have found or used and didn't need any more or they've come from a certain camp related storage house that shall remain nameless, they are free to us none the less.
Jack started the year off with Teaching Textbooks for math, but I wanted him to have a bit of book ciphering (sounds like prairie school) as well. We have the time in our day for both and I like the idea of pencil to paper in computation. How else can a homeschool kid get the phrase "SHOW YOUR WORK" emblazoned into his brain like we did as kids!
So while the last few years we've worked through Saxon Math we started this year out with a free to us book called "Multicultural Math." Thus far, he's worked in every area of concentration within mathematics in levels ranging from too easy to too hard (yeah, like, I can't even figure it out WITH the answer key!!). For the most part, I've been most thrilled with the diligence with which HE has had to pursue the topics... for instance, looking through examples to figure out how to solve a problem.
He's got a month or so left on the book before it's back to the "same 'ol" routine. But it's been a fun way to kick off the fourth grade year!