Hey all,
wow, this thread generated lots of good ideas, and I'll do some more reading in it later. For a fundraising and networking event we hosted yesterday in our office, I set up the following:
1) Colorful big screen showing real-time recent changes from the largest Wikipedias, using irssi and irc.wikimedia.org;
2) Firefox being controlled by a shell script to display random pages from several Wikipedias and some sister projects;
3) Firefox being controlled by a shell script to display Wikipedia articles about the March 4 Democratic primaries;
4) WikipediaVision: http://www.lkozma.net/wpv/
We'll have a permanent installation, and I'll probably keep 1) and 2) as they are, and replace 3) and 4). The real-time RC display is amazing to people -- so more stuff like that would be very cool.