First off, of course, check out www.unschooling.com
for lots on this subject.
My kids are 8 and 4. We don't use any curricula, and we focus on whatever the kids are interested in. I do buy the kids a few workbooks, and they use them as and when they choose. From time to time I look through dds math workbook to get an idea of concepts she hasn't worked with yet, and when she wants to, we sit down and go over some stuff. Usually she goes through a math book and just does fractions, so I like throw out some other ideas, too. A lot of unschoolers would never touch workbooks or anything else that smacks of school, but I think unschooling is more about philosophy and the way you approach learning-- natural, child-led-- than the tools themselves. DD mostly draws and reads about animals. She chose to learn cursive, so she practices it most days. Sometimes we spend a lot of time on the trampoline or doing laundry. (I don't want to get controversial here-- but unschooling is about learning from real life, and kids will learn what they see as important, as displayed in real life with there parents, so, yeah, we cook and clean, too, and talk about life, love, making babies, politics-- yes with an 8 year old--we go to the grocery store and balance the checkbook, because all that real life stuff is more important in the end than boring, old Tolstoy ever was anyway.)
My husband complains that we hardly ever "do" anything, but mysteriously my kids keep up with the school kids just fine. Ds is four and a half, and is beginning reading (because he wants to.) He'll be reading well by 5, but a lot of unschoolers wait much later to give there kids time to decide they want/need to read. Anyway, unschooling flows easily out of attachment parenting, because both philosophies are about giving kids what they need, and trusting them to determine what and when that is, rather than controlling them with scheduled feedings and crying it out, or scheduled study that ignores their real needs at the time, becoming a power play of "I said so!!"