I have seen someone give away both 17" and 20" ACD (the blueberry ones) on Craigslist. I even called the guy because it was local and was going to pick them up. I decided not to because I really had no use for the external displays but the point remains, people do give stuff away.
Also, it wasn't too long ago were a MR member was selling a bunch of iBook Clamshells for like $100 -- definitely would have suited your needs.