Szoter is a tool that allows you to take screenshots or use your own images. You can add annotations and text labels to the images. This would be useful for making posters, creating directions for online activities, making flashcards, and so on.
Szoter is available at http://szoter.com/#intro
Read reviews of this tool at http://www.freetech4teachers.com/2012/08/szoter-annotate-pictures-and-take.html#.UDAD6ESXSkA and at http://larryferlazzo.edublogs.org/2012/08/16/szoter-will-become-a-key-tool-for-ell-teachers