A few of my favorites:
The Teddy Borg - build your own fuzzy network interface. Some people have WAY too much time on their hands...
404 Research Lab - other ways to know that you are lost.
George Goble - this man is my IDOL!!! Learn how to go from a pile of charcoal to vaporized carbon in 2 seconds...
Unwise Microwave Experiments - I tried some of these and had to buy a new Amana - but it was worth it!
The Yuckiest Site On The Web - includes making your own snot.
-dave