This is a little bare at the moment, but will be added to in the future.
Darkstar's Woot!-off Checker has been around since 2006. Previous versions were fairly simplistic, storing the current item's data only. It has progressed to v3 and is more robust. It now stores historical data for each of Woot!'s 7 sites (woot, shirt, wine, kids, home, sellout, moofi). In addition, it also uses websockets to push data to the browser rather than using AJAX polling, though this should gracefully degrade should a browser not support websockets (thanks to socket.io).
A shift in approach
The most widely distributed version of dswoot was v2, which would only cache from woot on demand. Since it was only storing data for display purposes this was acceptable. In v3, however, this is no longer the case. This version uses Node.js as the central point. The node server will hit the application every 30 seconds to check for changes. If the cache has been updated it will broadcast the JSON to all connected browsers. Hitting the application every 30 seconds means it stays up to date whether or not anybody is using it, allowing for granular statistics and the possibility of sellout prediction.