OK this is bizarre.
But basically, what happens is on my MacBook (latest model) whenever I 'flip' a Dashboard Widget I hear a little noise for the duration of the flip: like a tiny continuous squeak noise. It's quite strange.
However, it only ever happens when the MagSafe cable is plugged in. WHY?! :'(
The noise appears to me emitted from the MagSafe area itself, but, there's not any other CoreAnimation or Quartzey bits that cause this to happen, it only happens with Dashboard widgets...
The noise is very quiet and you can only hear it in a silent room.
Edit: Running the latest Snow Leopard.