The Africa Map project, currently in beta, is an online map and data viewer created by Harvard University. The map combines data sets of numerous categories from a wide variety of sources, allowing thematic maps to be viewed and explored. The purposes of the project, according to the project web site:
Interact with the best available public data for Africa
See the whole of Africa yet also zoom in to particular places
Accumulate both contemporary and historical data supplied by researchers and make it permanently accessible online
Work collaboratively across disciplines and organizations with spatial information about Africa in an online environment
The Map Kibera project is an awesome example of community-powered mapping succeeding in a situation where commercial mapping providers would never venture: Kibera, the largest slum of Nairobi, Kenya with a population estimated at near a million. The project will train local residents to create community maps - using OpenStreetMap tools and techniques - and encourage the use of community-generated maps in relief and development efforts.