A friend of mine placed a yellow sticky to the bottom of a coworker's mouse, covering the optical feed.
YouTube has announced the new TEXTp rendering mode.
Everyone saw the Topeka thing I'm sure.
Did you play any tricks today (or were any played on you)?
*edit* And since we're at it, here's a list of well-known "public" pranks by radio stations, websites, etc.:
http://en.wikipedia.org/wiki/April_Fool ... own_pranks