I usually read slashdot. I make the window very small and I always have about ten million other things open so none of the titles on the taskbar are readable. (Just in case someone is standing over my shoulder looking at what other programs I have open.) If I know no one is going to be around for a while I play jigsaw puzzles from puzzlehouse.com.

When I can't do any of that and I'm still really, really bored... I find actual work to do. Sucks when that happens.