DIY optical communications network

Ronja is an interesting DIY design plan for building a set of optical 10Mbps transceivers capable of beaming information at 10Mbps up to 1.4 kilometers away. It's full duplex and costs less than $60. Ronja is small and easily transportable to remote locations for quick deployment of communication infrastructure. The technology simulates a LAN connection via LED transmission rather than using radio waves.

Transfer files between base camps, create village to village networks, or relay communications over multiple, cheap installations.

From the site:

Ronja (Reasonable Optical Near Joint Access) is a Free Technology (like Free Software) project of optical point-to-point data link. The design is released under the GNU General Public License: you get all the necessary documentation and construction guides free. The construction costs are minimal; it's probably the cheapest wireless system ever. The operation is reliable and immune to interference.