Just found something really cool:
http://www.sputnik.com
The concept is that people with 802.11b devices and broadband internet access become gateways. Your gateway then shares it's unused bandwith with anyone within range. Clients can access the internet whenever they are within range of someone running a Sputnik gateway.
Best of all, anyone who hosts a gateway gets free roaming on the system. Right now coverage is limited (looks like it's concentrated in the SanFran Bay area), but eventually as more people get involved there could be very good coverage.
I think this is one of the coolest things I've seen in a while. What do you think the odds are that it will catch on?