What are great alternative neighborhoods in the Bay Area?

I always love re-discovering where I'm from - and getting to know whole towns, areas, or even little tiny pockets that I wasn't even aware of. Upper and Lower Haight, Castro and Upper Market, inner and outer Mission, Telegraph in Berkeley, houseboats in Sausalito, .......... where else? What are your favorite little spots? I'm particularly interested in diverse places with village-like central areas, pretty residential areas, and a non-mainstream culture. It can be in the whole greater Bay Area.