Crowdsourced neighborhood boundaries in Boston, from Bostonography, based on an ongoing survey that asks people to draw the outlines of neighborhoods on a map. One nice feature of these maps are fuzzy edges; shading indicates points that less than 25%, 25 to 50%, 50 to 75%, or more than 75% of people think are in a given neighborhood. I think this is interesting even if you don’t know Boston; it’s fascinating how some neighborhoods have well-defined edges (major streets seem to play this role) and some just radiate out from a center.
This reminds me of an older project in San Francisco. Data here comes from Craigslist housing posts and an on-site form. The methodology is somewhat different in that it justs asks you to give an address and say what’s neighborhood it’s in. I would imagine this tends to give less straight-line boundaries. I could imagine someone in San Francisco thinking, for example, that Cesar Chavez is the boundary between the Mission and Bernal Heights (I actually had this conversation yesterday, because I’m moving into a place near there), but the same person might not use this as their decision rule when asked about a particular address in the neighborhood with which they were familiar.
What bothers me about using Craigslist housing posts as a data source is that “more desirable” neighborhoods tend to grow on Craigslist, as people with places for rent who are anywhere near a neighborhood border try to sort into the more desirable neighborhoods. In clicking through craigslist I saw stretches of the truth, some by only a few hundred feet (see above) and some by a couple miles (43rd Avenue is not the inner Sunset, it’s half a mile from the ocean!). The “good” neighborhoods tend to expand, and the inner Sunset has cachet that the Sunset has a whole doesn’t right now. For two years I’ve lived a couple hundred feet south (i. e. Oakland-side) of the Oakland-Berkeley border, but my landlord lists the place as being in Berkeley. And I have to give a hat tip to my old neighborhood in Philadelphia: this is West Philly, “University City” is a marketing scheme”.
I’m looking for a job, in the SF Bay Area. See my linkedin profile.
God plays dice 
I’d love to see something like this in the DC metropolitan area.
One catch that occurs here that may also occur in Boston is that not everyone recognizes certain areas as existing. I’ve characterized my own North Bethesda region as having “all the cachet of Bethesda with none of the admitting you’re really in Rockville”. And indeed the USPS still says that 20852 is “Rockville” despite it lying entirely outside the incorporated Rockville city limits. As far as they’re concerned, “North Bethesda” doesn’t exist.