I was happy to learn that some fine hackers have ported the excellent OpenWRT package to the very Zyxel (rebranded as Sprint) DSL modem I bought off of Craigslist for $20. Some of these Zyxel modems include an integrated WiFi access point, so in theory you could use Linux to control your DSL, act as your firewall, and push bits into the ether, all from one tiny little box.
Or, you could use OpenWRT and its capture page support to create an all-in-one internet hotspot! All you need is a phone line and a power outlet and you can create your own hotspot – nearly anywhere and for dirt, dirt cheap! In other words, its the perfect platform to create your own wireless network, anywhere.
The only catch is that this hardware seems to require the use of a serial cable to do the flashing. Still, it would be worth it to easily and cheaply deploy a wireless network across the city.