A woot off! is a quick sale for uber cheap...
they usually only sell one thing per day at woot! but during woot offs they usually sell a LOT of stuff for 24 hours, once something is sold out, they throw another one up there, so instead of having to wait until the next day for a new item, they just keep throwing stuff up there. And shipping is always only $5 with woot! They usually have a good graphics tablet for super cheap during woot offs, so I'm going to keep an eye out all day. I have an application called wootalyzer that tells me everytime there's a sellout and something new is posted.
They also have the ever-elusive Bag of Crap... which sells out in seconds. It can be anything, but they're always $5... sometimes it can be a flying monkey toy and sometimes it can be an xbox 360, you just won't know until the box gets delivered. We wait and wait and wait for the Bag of Crap, me and my man.