Reddit has some great city/state subreddits (obviously depends on how tech-friendly your city is.) http://www.reddit.com/r/austin is a pretty thriving place, for example.
Neighborhoods, in some cases, will have private groups. For instance, when I bought a house in my current neighborhood in Austin, the neighbors let me know about a private Yahoo group for this neighborhood. My neighborhood's population is just over 6,000 people. The Yahoo group has 1397 members and averages over 30 messages per day (!) Anything from "Can you recommend a plumber?" to "I have extra firewood" will show up there. The neighborhood association also prints a hard-copy newsletter that they deliver every month, which is sponsored by local businesses. (Note: We are not an HOA neighborhood--we just happen to have a pretty active population.)
Neighborhoods, in some cases, will have private groups. For instance, when I bought a house in my current neighborhood in Austin, the neighbors let me know about a private Yahoo group for this neighborhood. My neighborhood's population is just over 6,000 people. The Yahoo group has 1397 members and averages over 30 messages per day (!) Anything from "Can you recommend a plumber?" to "I have extra firewood" will show up there. The neighborhood association also prints a hard-copy newsletter that they deliver every month, which is sponsored by local businesses. (Note: We are not an HOA neighborhood--we just happen to have a pretty active population.)