"Unschooling isn't the absence of education. It's the absence of schools.

Public schools.
Private schools.
Even home schools.

There is no designated time for learning, no designated location where education takes place. Unschooling families see the world as an open classroom wallpapered with everyday experiences.

Kids express an interest, ask a question or wonder out loud whether fish breathe. Parents help them find the answer and foster discussions.

But they don't push."

My family has been moving closer and closer to unschooling. At this time I only formally teach writing and math. Reading, literature, science, art, and technology and other topics are off and running on 4 legs.
We are going to the Live and Learn Conference in a couple of weeks. I might make the complete jump soon - I am very interested in meeting the older unschooled children.

A fair article on unschooling