Jing is a free software that you can download onto your computer which allows you to take pictures of your computer screen. This is really useful if you want to show students how to do something on the computer, like access a resource on Moodle. I like Jing because it allows you to add arrows and text to an image, to make it clear exactly what you are trying to point out or say - I have used Jing to illustrate my instructions in this post.
The first 4/5 minutes or so of this video will show you how to download Jing onto your computer.
Here is a video I have made to show you how to use Jing once you have downloaded it onto your computer.
Can you recommend any other tools to do similar work?