Surprisingly, there aren’t a huge number of screenshot tools for Linux. Luckily, they don’t need to be, because the feature-rich Shutter is about as awesome a program as you can ask for.
Mac OS X already offers a means of capturing screenshots with a few keyboard shortcuts, but if you want to do a little more you have to grab a third-party tool. Of the many available, Skitch is our favourite for its many annotation tools and instant-sharing options.
Windows: Taking a single screenshot is easy, but if you need to take several quickly, the Automatically Take Screenshots app can take as many as you need as frequently as you choose.