If anyone here needs a real demonstration of an interactive, live demonstration of cool interactive programming, check out the piano exhibition of this programmer. :-) It's a screen cast of a programming session that results in music generation in real-time, live.
Check out the environment used to create this by examining
http://impromptu.moso.com.au/.
Oh, and by the way, it's Scheme. ;-)
http://homepage.mac.com/digego/study_in_keith.mov