Here's a joke which I am telling friends around nowadays and so far only two people laughed on it.
A policeman pulls Werner Heisenberg over on the autobahn for speeding. Policeman: "Sir, do you know how fast you were going?" Heisenberg: "No, but I know exactly where I am
Also, I found an excellent collection of Riddles and Logic Puzzles on UC berkeley's website, with a very nice slogan.
[hardcore tech-interview style riddles, not gaussian elimination logic puzzle fluff. updated regularly. millions served! ]
Here I also disovered that YABB forums software is cool!