"Hmm. I wonder. I was thinking of dancing trees. Now I'm wondering what's next. Screaming trees. Yeah. That's got to be the answer. Screaming trees." - private notes by Hans Reiser, filesystem designer and a convicted murderer

(OK, that's a fake quote. This one is real:)

"Trees have their roots pointing up. And if you cut a tree apart, you get a forest. No, I'm not drunk." - one of my computer science profs, on data structures