Check out Capture Fox at https://addons.mozilla.org/en-US/firefox/addon/8090/. This wonderful free add-on makes capturing your screen incredibly easy to use. A small icon will be displayed in the bottom right corner of your screen and with the click of a button, you'll be capturing your screen! You have options, as well, and you can include sound. For instance, you can choose to capture the whole screen or just the Firefox window. If you do any professional development or teach, this is the tool for you! Add these to your classroom webpages or training pages and you'll have a much more supportive learning environment that is bound to improve understanding at all levels!!
Thanks to Leidiana for sharing an excellent Math tool, as well. Transtar is a reflections and transformation activity and can be used for free! I've used Capture Fox to capture the game in action! :)