I am actually a big fan of Apple’s Dashboard, part of OS X 10.4 (Tiger). Some people call it all fluff, but I don’t agree. I find it very useful. I do limit my widgets to just the essentials though.
That being said, I’ve come across a widget that borders on the totally useless, but I love it anyway. It’s SimpsonBot, and all it does is display quotes from The Simpsons… possibly the greatest show ever made.
UPDATE (8.02.05): SimpsonBot has been updated to version 0.8. The update includes more quotes and a slightly different design.