Last year a few of us here at The Open Planning Project built BlockPartyNYC.org. This project was done for Transportation Alternatives, mainly to promote their party sponsorship program. A sponsored block party received consulting on solutions to community problems like traffic, speeding, and noise and air pollution.
For this year of block parties in NYC, we have plans to make BlockPartyNYC the main hub for all 3000 NYC parties. We plan on receiving data feeds from Community Boards as they approve block parties and, in turn, advertising relevant parties on Community Board sites. We plan on having more advanced mapping, facebook integration, and other features. See the full specification.
If you're a developer out there and would like to help out please get in touch by emailing email@example.com. It's a fully open source project built in pylons and can be reused for other events. For example, last year we also used the software for ParkingDayNYC.org. Thanks and stay tuned.