We use books and other schooly things, but the hands on, spur of the moment learning seems to work best. This would actually be called unschooling - something I've looked into, but can't quite let it all go - "it" being the school mentality.
So Sweetie got the idea to trace our shadows with chalk on the driveway. He embellished them with hair and hats. He drew curly locks on Lovey and for whatever reason, Lovey didn't want his curly locks, so Sweetie turned them into ear muffs. This suited Lovey just fine since he wore ear muffs to see the Monster Trucks.
The great part about Homeschooling is that everything presents an opportunity to learn. Sweetie loved how TALL he was at that time of day, so (ding ding-science) a discussion of the earth rotating around the sun ensued. Through this discussion, he decided that we would have to just draw (ding ding-art) Dad in because if we waited until he got home from work at 6pm (ding ding-math), he would be standing "opposite" of us. (ding ding-math/science again) See how this is working. We made Dad extra muscle-ly. :-)
Even if you don't/can't homeschool, make sure and take advantage of these learning opportunities. Your children will learn and you will learn from them.