So a small company called Merkai Networks (www.merkai.com) is releasing a $59 wireless 802.11G access point. No big deal. The thing is that node has some mesh capaibilities baked right in. This allows it to extend existing muni wi-fi networks as well as to bake your own mini wireless mesh.
It all still has a way to go but add the above to the fact that its based on opensource software and it really opens up some interesting options.