Seattle Wireless ( http://www.seattlewireless.net/) has taken on one of the most ambitious projects of any community group: they intend to build a fully routed Metropolitan Area Network, independent of any commercial service provider. To this end, they are setting up their own top-level DNS domains, allocating private IP addresses, setting up backbone nodes, and managing the roll-out of the network so that any wireless node will be able to reach any other, without ever needing to pass packets over a commercial network. As any backbone node is able to provide Internet gateway services, wireless clients can also access the Internet regardless of where they may physically be located in the city.
As the entire wireless network doesn't ever rely on the wire, it keeps the operating cost of the network fixed, and also could provide valuable communication services in the event of a major disaster (Seattle isn't exactly known for its stability, in many ways). Seattle has some unique geographical advantages that may help this approach: relatively few trees, many tall buildings, rolling hills, and a high concentration of technically capable alpha geeks. I'm sure the coffee doesn't hurt, either.
Their web site provides a terrific wealth of information, from network routing theory to antenna design. The Seattle Wireless web site was launched in September 2000. Since then, they have been mentioned or featured in over 35 publications, ranging from Wired magazine to Le Monde, a major newspaper in France. They also have a huge mailing list following and hold regular meetings. They are making things happen in the Great Northwest.