Using an arduino nano, a rf23b (http://www.hoperf.com/rf/fsk_module/RFM23BP.htm) wireless module (or anything like it) and a solar panel to build a mesh network node that can be used to quickly deploy wireless networks.

The connection between the nodes will be serial, a endpoint will have an additional wlan module connected so it will be possible to use the mesh network for normal wlan enabled devices.

Update:

The code for a basic rf mesh chat app is now on github:

https://github.com/greygoo/rfchat
https://github.com/greygoo/rfmesh