The MIT swap is wonderfully random. As time passes, less of the old stuff shows up (as is inevitable), but every so often, someone appears with a truckload of treasure. The last time I was there (a couple of years ago) I picked up a box of prototype game cartridges for the VIC-20 from someone who was a failed game developer for that platform. These carts never made it into volume production -- they finished development just as the C-64 hit store shelves.

Great flotsam.