Freifunk
Freifunk.net is a german-speaking non-commercial network dedicated to the creation of wireless community networks (open wireless mashup networks).
In practice the networks are mostly used for the sharing of (free) internet access.
It's a knowledge base, for example about hardware, and a collection of free local networks to connect them and to promote the idea of sharing (money) free internet access.
Beneath the portal start.freifunk.net, there is an open wiki.