Someone Made Wikipedia for Just Your Neighborhood...
Ed Jefferson built a site that shows you Wikipedia, but only the parts you could walk to. Local Wikipedia describes itself as "Wikipedia, but only for things a half hour walk from you."
It works because a lot of Wikipedia already knows where it is. The site uses geocoded pages only, pulled from Wikipedia's geosearch, which MediaWiki documents as a search "for articles around the given point."
The script behind Local Wikipedia sets that half-hour walk at 1.5 miles. If fewer than 25 things are that close, it reaches out to the nearest 25 within about six miles, and it stops at 500 (sorry, downtown Manhattan).
The fun is in what people turn up. On Hacker News, one commenter hit "random article" three times and got "three weird stories I didn't know about the history of places within a few blocks of me in Portland, Oregon."