I read an interesting article recently in Wired magazine about a Spanish start-up, Fon, who are promoting a free WiFi Community.
The principle is simple - share your WiFi Internet connection with other users and you can use theirs wherever you spot one in range. Initially the service is being offered to people and organisations willing to share their connection for free ("Linuses"), This will extend later also to "Bills", someone who wants to make some money from opening up their connection. (Bet you can't guess where the names come from!)
To join the community you need to have a compatible router or cable-modem. Currently only some Linksys models are available, but you can also buy on these on the site at a discounted rate of $25 / €25 (while stocks last).
You then need to install some FON software onto the router, register your connection and you're away. Fon ask for your postcode, so that you can easily look-up where the nearest Fon hotspot is from the Fon Map, (which overlays Google Maps).
They also seem to have addressed security reasonably - the Fon blog explains how a separate VLAN is created on your wireless connection, segregating 'public' wireless from 'private'. I'm not sure yet though if you can also throttle the bandwidth you make available publicly using the software - I'll let you know as soon as I replace my now-ageing 11mbps Intel WiFi with a Fon-friendly Linksys one!
Throw a wi-fi phone into the mix and mobile telco's may have another thing to worry about!