Unschooling is not exactly a method of homeschooling, but is within the same scope of concept. The child is kept at home and taught by a large variety of means.
The way unschooling differs from homeschooling is there is no set curriculum. The student is taught through more kinetic learning methods and are encouraged to be their own guide.
This is not to say that the unschooler doesn't have structure. We all find our own groove and sometimes that groove is very structured, even if it is non-traditional.
If you watch a young child before they are school aged, you will see them constantly learning new things. They are like sponges. That doesn't fall away and die as they grow. We have simply fallen into the way society has taught us that we must do things. One does not require a workbook to learn math. Apples and oranges can do the trick.
Information and support on unschooling can be found at www.unschooling.com.