In one of my crazier moments, I recently purchased a surplus Schauf LED message board. It's a pretty nifty piece of hardware - it has two 2x16 character displays (one on each side) that can also go into a 1x8 mode with double-sized characters. The two sides display the same message; I have not checked yet whether they can be addressed individually, but I suspect not. The innards are OEM'ed by PolyComp, and they talk to a PC over an RS-232 serial link, via a proprietary (but fortunately fairly well documented) protocol.
Currently the sign is hanging in Project Club and displaying headlines from some RSS feeds (Newsvine, Ars Technica, and Case News, if you must know). It's also possible to send a message to the thing using AOL Instant Messenger, though I'm not going to publish the screenname on this blog. :) The software to accomplish this is written in Ruby, and, on the off chance that any other Ruby programmers happen to have one of these signs, I've put the code for communicating with the sign on opensource.case.edu.