A flea market for electronics enthusiasts: all manner of junk for sale, from vacuum tubes to DOS mailing-list programs. It's generally a good idea to get there before dawn, as the Really Good Stuff disappears early.
This used to be at Foothill College, but has been relocated to Sunnyvale, at least for 2004. Location is 11th Avenue and C Street, out behind the Blue Cube.
Details (including directions) are here.