Here are some great jokes selected from some of the discussion in this slashdot posting. Some posted there were from funny2, and some from the book Absolute Zero Gravity: Science Jokes, Quotes and Anecdotes. See also this site, with a nice large database. Enjoy!
Q: How many Heisenbergs does it take to screw in a light bulb?
A: If you know the number, you don't know where the socket is.
Q: How many quanta does it take to screw in a lightbulb?
A: One and a half.
Q: How many consulting engineers does it take to change a light bulb?
A: One, that'll be $50 please.
Q: How many nuclear physicists does it take to change a light bulb?
A: One, he raises it into place and the world revolves around him.
Q: How many mathematicians does it take to change a light bulb?
Q: How many Pentium owners does it take to change a light bulb?
A: 0.99987, but that's close enough for most applications.
Q: How many Microsoft engineers does it take to change a light bulb?
A: It burned out? You must be using a non-standard socket.
Q: How many Microsoft engineers does it take to change a light bulb?
A: None, they merely change the standard to darkness and then they upgrade the customers.
Q: How many AOL users does it take to change a light bulb?
A: Two, one to screw in the light bulb, and one to watch him to make sure he doesn't say 'nipple'.
Q: How many Apple employees does it take to screw in a light bulb?
A: Ten - one to screw it in, two to design the icon, four to design the T-shirts, and three to come up with the code name for the project.
Q: How many software engineers does it take to change a light bulb?
Q: How many maintenance programmers does it take to change a light bulb?
Q: How many software testers does it take to change a light bulb?
A: None. "We just recognized darkness, fixing it is someone else's problem."
Q: How many C++ programmers does it take to change a light bulb?
A: "You're still thinking procedurally! A properly designed light bulb object would inherit a change method from a generic light bulb class!"
Q: How many Java programmers does it take to change a light bulb?
A: One, to generate a "ChangeLightBulb" event to the socket.
Q: How many Windows programmers does it take to change a light bulb?
A: Seventy two. One to write WinGetLightBulbHandle, one to write WinQueryStatusLightBulb, one to write WinGetLightSwitchHandle ...
Q: How many data base people does it take to change a light bulb?
A: Three: One to write the light bulb removal program, one to write the light bulb insertion program, and one to act as a light bulb administrator to make sure nobody else tries to change the light bulb at the same time.
Q: How many IBM employees does it take to change a light bulb?
A: Fifteen. Five to do it, and ten to write document number GC7500439-001, Multitasking Incadescent Source System Facility, of which 10% of the pages state only "This page intentionally left blank".
Q: How many technical writers does it take to change a light bulb?
A: Just one, provided there's a programmer around to explain how to do it.
Q: How many marxists does it take to screw in a light bulb?
A: None. The seeds of the revolution are in the light bulb itself.
Q: How many Australians does it take to change a light bulb?
A: Twenty-one. One to hold the bulb and twenty to drink beer until the room starts spinning.
Q: How many college students does it take to screw a lightbulb?
A: I don't know, will this be on the test?
Q: How many buddhists(sp) does it take to change a lightbulb?
A: Two, one to change it and one not to change it.
Q: How many clowns does it take to screw in a lightbulb?
A: As many as they can fit inside
Q: How many ADD kids does it take to screw in a lightbulb?
A: Wanna go for a bike ride?
Q: How many Freudians does it take to screw in a lightbulb?
A: Two, one to screw in the lightbulb and one to hold the pen1s... I mean ladder.
Q: How many feminists does it take to change a light bulb?
A: That's not funny.
Q: How many people does it take to screw in a light bulb?
A: Two, the same number it takes to screw anywhere else.
Q: How many science fiction writers does it take to change a light bulb?
A: Two, but it's actually the same person doing it. He went back in time and met himself in the doorway and then the first one sat on the other one's shoulder so that they were able to reach it. Then a major time paradox occurred and the entire room, light bulb, changer and all was blown out of existence.
Q: How many teamsters does it take to change a lightbulb?
A: Forty... you gotta problem with that?
Q: How many internet mail list subscribers does it take to change a lightbulb?