StringThing
Spin and jerk a hanging rope such that it is excited into a variety of modes.
This is from a year ago but I didn't get around to posting it before.
Videos available on the Internet Archive:
You can get the code as part of dr1 here:
git clone http://code.mathr.co.uk/dr1.git
Or browse dr1 on Gitorious dr1 on code.mathr.co.uk.