Most homeschoolers realize that children don't just learn between the hours of 8 and 3. Kids learn all day long. My daughter learns about history and geography at bedtime when I read to her from Little House On The Prairie. She might learn math at the grocery store. While we have formal learning, it doesn't stop there. Since I'm her sole teacher, if I can find ways to integrate learning in the rest of my daughter's day, I will.
The same is true for age. Kids don't start learning at 5 and know everything they need to know by the time they turn 18. They start learning at birth. In fact, they learn at a more rapid rate when they are younger.
Although my homeschooling efforts are currently focused on my daughter, I also have an 18 month old. As he gets older, I can do more "formal" learning with him. Not really formal because we don't have a curriculum that we use yet, but I can tell him what a train is, or a fish or a bird, and he'll pick that up from me.
I've been trying to teach my son sign language since he was about 3 months old. I wasn't expecting him to sign with me at 3 months, I just wanted him to start getting used to it. I haven't been the most consistent person in the world at it, but I kept on plugging away at it.
At around a year old, ds started picking up a few signs. He first signed dog, then he learned fish. He started signing milk and pointing to his mouth to tell me that he was hungry or thirsty (I just had to guess). It's very nice to have your baby be able to tell you what he wants.
Now he can tell me a lot more about what he wants or is thinking. Just today he made the sign for water (he doesn't do it correctly, but I know what he's trying to do) and I knew that he wanted something to drink. He will also make that sign when he sees a lake. We went for a walk and he heard an airplane, and made the sign for plane. Just a couple of days ago, he heard dd running the water in the bathtub to get her hair wet, and he made the sign for bath.
I have to thank the people at Signing Time for their great DVDs. They have catchy tunes and are made with children in mind. I'm glad that our library has them, although they tend to be a hot item and are often gone. Our local PBS station is now showing Signing Time on Sundays, so I have Tivo set to record it.
Dd has picked up on sign language too. She's getting pretty good at it. :)