My friend and I have been having a very similar discussion thread of late, although we've been using "The Volvo-Subaru Corridor" as our name for these types of areas. We both live in one (I'm in Minneapolis, he's in Berkeley) and can spot at least a few commonalities (some of these his):
Large lesbian population
Reading in public (people will sit on outdoor benches and read; libraries are also well-patronized)
Durable, older, smaller cars (Volvos, Subarus, Toyota pickups, Honda hatchbacks, Volkswagens) or hybrids
Eastern/non-conventional religious spaces (zen centers, UU churches, etc.)
Neighborhood density around 6000-12000 people/square mile. This results in a housing stock of side-by-side two-families, courtyard apartments, and multi-room storybook Victorians that is specifically suited to communal-but-not-crowded living arrangements (co-ops, communes, cohousing, poly villages, extended families)
Heavy cross-promotion of local businesses/bands/events
Bright colors (of houses, storefronts, clothing, cars)
Major wilderness set-asides or other large urban parks
Large percentage of non-TV households
Young children are welcome everywhere and seen often with their adults: at restaurants, at museums, grocery shopping, playing in parks. Children in these sorts of communities also seem to spend far more time outside playing than their suburban counterparts.
Independent auto-repair shops with names like "The VW Hospital" and "Lazlo's Foreign Car Repair" that have been in business since foreign cars first became widespread in the US in the 1970s. They specialize in a few makes of cars and are often run by curmudgeonly old guys who rarely smile and deliver stern lectures whenever you bring the car in for repairs.
Practitioners of "eccentric" sports: curling, frisbee golf, Aussie rules football, geocaching, snowshoeing, vintage base ball, adult kickball, roller derby
