Jing is a similar software with Snagit, both developed by the same company, designed to make screen captures.
Unlike Snagit, Jing is free and does not includes all features of Snagit, but can be used with success for quick screen capture and basic editing options.
With this tool you can grab an image from your screen (entire window or custom region) and add text, lines, arrows or other shapes. Save it and use it for presentations and tutorials or share it on a social network. Also, can record videos up to 5 minutes.