A whole downloadable book, under Creative Commons License, for people to build their own wireless networks, for very little cost in developing nations. Very cool.
Alas, the two chapters on Networking were more instructive than almost anything else I remember from my graduate degree in computer science. (The anything being the great Mahjong games on those high end SGI workstations.)
Link here. Maybe if you are traveling anytime soon, print a copy out just in case you meet someone that you could give it to.
HT - BoingBoing