WLAN

"The WLAN standard 802.11b has two modes, the infrastructural mode (for Access Points) and the ad-hoc mode (also called peer-to-peer or computer-to-computer mode, depending on hardware/software vendor). When a wireless network is set-up in the latter way, each node can connect to each other node as long as they are within range of their radio signals. Since there is no privileged place in the network, each node carries out functions of switching data packets around, acting as a router and Internet gateway. Since every node shares this task of switching packets around, the overlapping radio coverage of all nodes together forms a single wireless cloud." (http://theoriebild.ung.at/view/Main/WirelessUtopia)

See how it is used by the Free Networks Movement