I have been really truly inspired by Urban Homestead in Pasadena, California. This family of four has a high efficiency "farm" in the middle of the concrete jungle. On a fifth of an acre they house goats, chickens, ducks, bees, themselves, and still produce about 6,000 pounds of fresh produce in their gardens. I won't even get started on the outdoor solar shower or their homemade bio-diesel, but these folks are amazing.
They really do prove that even with just a smidge of land, anyone can lead a self-sustaining lifestyle.
Check 'em out!