I recently bought myself a Raspberry PI and while it is advertised as a cheap motherboard the whole deal works out quite expensive, and the idea that it will be ideal for the 3 world is not exactly true.
Cost of Raspberry PI model B
R540.00 Include delivery http://za.rs-online.com/web/
R50 HDMI cable
R1400 small HD tv to use as monitor, yes they do say you can use a tv with avi but it is such a pain to get that to work .
R40 SD memory card
R50 Blackberry Charger to use to power MOBO
R250 cost of downloading the software
R100.00 Raspberry case
Excluding the TV which I had already
Loading the Raspbian OS Image to the card can be done through dd on linux and winimager on windows. Once done there is still quite a few tweaks once has to do to get it up and running.
So Raspberry PI is more of a hobby item for geeks and nerds, but as a tool to teach third world programing cheaply, not quite there yet.