Why do computer scientists often confuse Christmas with Halloween? Because Dec 25 = Oct 31.
Two strings walk into a bar and the bartender says, "What can I get you?" The first string says, "I'll have a beerKJLASdp)8AIDnhas89d3"¤"#¤(/)a8dsd79". "Please excuse my friend," the second string says, "He isn’t null-terminated."
And the obligatory one: There are 10 kinds of people in this world: those who know binary and those who don't.
We also have some awesome songs in our songbook at the CS dept here, but they're all in Danish. I can't think of any more jokes right now.