Hardware Knowledge
As I stated above, you are going to be working with hardware in a very different atmosphere from home both figuratively and literally. Literally, the environments in which most computers find themselves in the developing world is about as hostile to the computer as outer space is to a human being. Humidity, dust, corrosive sea air, bugs, all of these will wreak regular havoc on your hardware and there are no 24-hr box stores you can just run to for spares.
So make sure you bring over your best hardware troubleshooting, diagnostic and repair skills. Make sure that when something breaks, you can know for 100% certain which part of the computer is actually broken. This minimizes the need for multiple trips or uncertain suggestions for what the organization may need to pay for. Remember, parts are expensive and at this early in the stages of ICT for development most people would rather live without the computer as they have been for hundreds of years than fork over 3 months’ living wages for a stick of RAM. In short, understand as thoroughly as possible hardware troubleshooting so that when something breaks you know exactly how to fix it.
Also be able to assess the environment and know the best pro-active methods for protecting your machines. Prioritize budgeting in Un-interruptible Power Supplies (UPS) for the computers, and explain why computers need them, even when the day to day task of a UPS seems so menial. Be able to explain the impact dust, water, bugs and other nasties have on hardware. Be able to educate others in your area that a computer is a tool that needs to be treated properly just like knives or hammers or bicycles and that they are not flawless; that they may get old and breakdown over time. Make people understand that though computers are a continuous investment the investment will be worth it in the end (though long-term investment will be one of the hardest concepts you will have to teach in any field, no matter where you go).
One Computer at a Time 
Thanks, that was refreshing to see again that you’re thinking about a lot of the stuff I’d been thinking about in Tanzania. I would expand from just UPS too: I think that AVS and other line conditioning can be more cost effective for labs.
http://ttctip.wordpress.com/2009/09/21/umeme-uchafu-and-you/
I like FOSS CloneZilla cloning software but I haven’t tried PING.