CloudShot, which is available for Windows machines, is a screenshot app which automatically uploads images to any folder on your system - and that includes Dropbox folders too. Dropbox has become a very popular tool in a very short period of time. Any solution that connects to it or helps users interact with it, is also going to see some exposure and ultimately usage.
The CloudShot screenshot app has all of the expected features and a few others which definitely make it stand out including the ability to take screenshots of a specific region, windown, menu or tooltip. CloudShot also enables users to use its application with multiple monitors. There's even a history which provides the ten most recent images.