I use iCal's onscreen alarm a fair bit at work to remind me of meetings and tasks and so on. As I am brain-dead when it comes to remembering things, I keep the alarm window up on the screen for a little while, until I can get to the task. But that little freakin' "visual buzz" the clock does was driving me crazy.
It turns out you can control-click on the clock itself and select Stop, as seen at left. Ah, Peace on Earth!
[robg adds: Another great example of a hidden feature that doesn't seem to be documented in the provided help file ... great to know it's there, but why won't Apple tell us about these things?]

