As mentioned before, radio is the killer ap for much of the developing world. At the same time, creating communications systems which can run off-grid is a real challenge. Here's a project, RURANET, which tackles two problems at once, creating a locally-run, solar-powered radio network in Niger:
In Bankilare, in southwestern Niger, many of the 2000 inhabitants and about 10,000 nomads in the vicinity do not have access to electricity, telephone or clean water. Radio is the primary source of news and information, but few can afford a radio or, more significantly, the batteries it consumes. The villagers often have great difficulty receiving the signal from the national radio station ORTN, which also does not broadcast in the local languages.
[T]he residents of Bankilare built their own radio station, which runs on solar energy, and broadcasts programmes in three local languages. A growing number of villagers have access to solarpowered or wind-up radio receivers that require no batteries. Whats more, through the station, local farmers can obtain a variety of useful information, including weather forecasts, drought and pest alerts, and market information, downloaded from a satellite.
The Bankilare community radio station is one of the first in an ambitious seven-year programme to build a rural radio network (RURANET) of 160 selfmanaged, solar-powered broadcasting stations in Niger. Currently, more than 70 RURANET stations are fully operational.
RURANET gets its news via the bird, free, on donated satellite radio receivers, but it could just as easily come in other forms, as Ethan has pointed out.