spinner
BEHOLD!
Actually, that's just a Javascript version I made of the goodness that is spinner. There is a standalone Javascript version and a C code version. You can also find a proper tarball below. The code is ugly, but the output is so mesmerizing I didn't bother to clean it up. It's all public domain, so put it on your website or whatever. I'd like credit, but whatever. The idea is so simple, it's not really necessary.
Oh, you'll need ncurses, but who doesn't have that?