A lot of scientific and/or Open Source projects would probably be very happy to get server hardware like that. Pick out a handful or two of projects that you enjoy, have enjoyed in the past, or just find important, and ask them if they want any of it - they'll most likely be very happy!

First of all, keep it simple. Please, don't flood the youth with all sorts of things they wont understand... I mean, pointer arithmetics can fool even professional software developers every once in a while. My recommendation is to go with something that's made for young people - Ruby and Hackety Hack is a great example of that; Ruby because it's (usually) quite easy to understand what a program does simply by reading it out loud, and Hackety Hack because it's... well, made to solve your exact problem. Plus, Ruby makes a great platform to later demonstrate OO and what have we. But whatever you end up with, please, for the love of god, don't use a statically typed language - it just makes the learning curve unnecesarilly high for no particular reason.