Any process which operates on itself, or the results of its operation, is recursive. This is one of the most powerful system dynamics.
When you get mad at yourself for being mad at yourself, you can tell it's pretty bad, and when you're celebrating because you're celebrating, it's hard for things to go anywhere but up.
Vicious cycles and virtuous circles
Doctor Who's Tardis inside itself
Also see http://ourpla.net/cgi/pikie?ReCursion (offline, see:)
Blog entries tagged with recursion
Other cards tagged with recursion