The single best thing we could do to help African nations - and in fact, the entire developing world - is to cut agricultural subsidies in the Western nations. We cripple the only chance they have of an export economy, all so rich corporate farmers can get richer (they get about 65% of the subsidies, compared to small farmers who could still be subsidized provided they don't export - France is moving this way).
The second best thing we could do is expand the electrical grid.
<a href="http://www.geni.org/globalenergy/index2.shtml">
http://www.geni.org/globalenergy/index2.shtml</a>
The third best thing we could do is stop sending food aid to countries with famines. It's harsh, but we keep people alive who can't be fed by the land they're living on. We create a cycle of famine and dependence.