The community wireless phenomenon is happening all over the globe. There is a good list of projects up at http://www.toaster.net/wireless/community.html. A few of the major networks (and our humble Sebastopol co-op) are listed below. If there isn't a community group in your area, start one yourself! I was certainly surprised at the broad range of people interested in setting up communications. Get the word out, start a mailing list, and get connected to your community. The resources that a community can pull together for a common project are astounding. You simply have to do it!
Seattle Wireless (Seattle, WA)