If you've ever kicked yourself for missing a price drop on a game on the Steam platform you'll love Steam Alerts. All you need to do is list what games you want, how much you're willing to pay and your email address -- you'll be notified when the game drops below your maximum price.
Clicking on the history button beside each game will give you a price history for the game in question for the past two months. If you're not searching for a particular game, the index page of Steam Alerts will display games that are currently on sale and new releases. The official Steam store sort of does that as well, but without alerts and a price history feature I'd rather use Steam Alerts for discovery.
It's annoying to miss sales on a desired game and now we have the technology to avoid this first world problem. The hat tip goes to The How-To Geek for first discovering this handy webapp.
SteamAlerts Notifies You of Game Price Drops [The How-To Geek]