Woot's general modus operandi: sell one item every day. The new item is posted at midnight Central time. The quantity is unknown (there could be 5, or 5000). If it sells out, you are out of luck... you have to wait until the next day. It is usually a screaming deal, you can buy up to three, and every order has $5 shipping (regardless of what it is and how many you order).
Woot also periodically offers a highly coveted item called a Bag O Cr**. (aka: BOC, Beverage of Choice, Bride of Chucky, and so on...) BOC's are always a buck (plus $5 shipping). They recommend you order three, so as not to waste shipping. And yes, these are a super screaming deal... if you are the type of person who waits until Christmas morning to see what's under the tree, and don't mind the ancillary stuff you didn't necessarily need or want, but it's kind of cool to have. We have purchased 3 BOC's - and have received items including stuffed panda bears, a portable CD player, an 8-pack of Anne Geddes calendars, and a "pleather" briefcase. So... while it's not stuff that would generally make it to my shopping list, none of it was bad to have around (and the kids liked the pandas!) and was worth "risking" a dollar.
TODAY happens to be another fun feature - it's a Woot-off. This is when all the same rules are in place... except that when an item sells out it is quickly replaced with a *new* item. Woot-offs can last for hours or days, depending on how long it takes to sell through everything. Adding to the suspense, they put a status bar below the item so you can see what percentage of the quantity (a secret) has sold so far. Since the new item isn't posted until the previous one sells out, there can be long or short timespans between each new item... you just never know.
Happy Wooting, and have a Wooterific day! :)