Greenshot is a free image annotation tool that allows users to capture screen shots or select an image file for annotation.
To download Greenshot or to get more information go to http://getgreenshot.org Greenshot help is located at http://getgreenshot.org/help
Make sure to click on the Downloads link because there are other advertisement downloads on the screen. See below:
Using Greenshot for annotation:
Select the image you want to annotate from the file and select the Open in image editor option.
Greenshot has all of the standard annotation tools. Annotate the image as desired and then “Save as”. Do not just save the image or you will lose the original, un-annotated image.