LittleSnapper from RealMacSoftware is on sale for US$5 until January 17 through the Mac App Store. The app normally sells for $25, and it had sold for $40 before the Mac App Store.
LittleSnapper is a screenshot management application. Think of it as a combination of Skitch and an iPhoto-like application for managing your screenshots.
We covered LittleSnapper before, back when it was released in 2008, if you want more information about the app. You can also download a demo version of the app from RealMacSoftware's website.