I found these easter eggs of softwares while browsing some sites, i tried a few and they actually worked
Picasa Teddy Bears
How to find it: In Picasa, press Ctrl+Shift+Y. What you get: Your photo library taken over by teddy bears! Keep hitting the key combo to add more bears. [via PC World]
Firefox Kitchen Sink
How to find it: In Firefox 2 and higher, type
about kitchensink (no colon in there, unlike about:mozilla!).
Correction: Looks like this one only works in the Firefox 3 beta. Apologies! What you get: An automatic redirect to an animated, ASCII art kitchen sink.
There are a lot more just a google search away :).