It's a crazy mixture of burning man, a music festival, and a nifty tech fair. It's a great blend- watching the burners and the non-burners (... like my parents) interact was awesome.
I was one of the organizers two years ago (which was the last time it was at Ames). Even though the day of was sort of frantic for us, I had a blast. Music everywhere, things throwing fire, lots of great geeky exhibits. And it's all in and around some hangers just off the Moffett Field runway!
I'm not directly involved this year, but many of the same people that ran it then are working on it now; I expect it to be awesome again this year. Hopefully my mass of positive adjectives encourages you to check it out this year. Heh.
Some nifty pictures (not mine):
http://www.flickr.com/photos/spacemansam/2422866234 (NASA Ames Center Director Pete Worden in costume as a Soviet general!)
http://www.flickr.com/photos/smashz/2412213920