The above writeup describes Free Geek very well, although some details have changed (the minimum processor we now use is a P133, for example). Free Geek is also constantly expanding and trying new things, including a brief experiment with cinema, but the basic idea remains the same: taking something that would otherwise go to waste and turning it into something useful using volunteer labor. And teaching people something at the same time.
That being said, I would like to talk about what Free Geek means to me. I am a fairly regular volunteer there, and I've seen somethings there that have really shown me about the way that people can associate together. In an interview about Gracie's, another important Portland institution, one of the reasons given for founding Gracie's was that it provided people a place to associate with each other without having to consume. It was noted that most of the socialization we do in our society revolves around economic consumption. Gracies was invented as a place where socialization could be neutral. In my view, Free Geek is much like this, only it takes it one step further. Instead of socialization being neutral, it is instead productive.
Free Geek's headquarters is called "the Community Technology Center", which, if you overlook the fact it sounds like a Scientologist Front Group, shows the entire thrust of the program: whereas some people may think that communities left to their own devices would simply while away their gears in comsumption, and that technology and production have to be thrust on them from above, either by neccesity or social coercion, the premise of Free Geek is that normal human culture, and simply the ways we normally interact with each other, can be harnassed to produce things. Many things could be produced: movies, plays, quilts, scarves. Free Geek just decided to take the challenging job of producing something very material. But at base, the message of Free Geek may be that production of something as complicated as computers can be done by a group of people as easily as they would make a dish for a potluck.
Free Geek shows that human communities are naturally productive.
And that is the pretentious reason why I spend my free time pasting 5 digit numbers on 8086s.