Tool: Screencast-O-Matic

Requirements: Computer w/ Internet; microphone if you want to capture audio.

Cost: Free

Anything you do on your computer, you can capture as video using this tool! The tool records all your mouse movements, your screen changes, and even your voice. Then, you can choose to either upload the file to the site or download it to your computer (or both!).  If you put it on the site, you get a link to the video that you can give to people. If you download it, it's in .mov format and you can do whatver you want with it.

Example Screencast-O-Matic

A screencast demonstrating how to use the tool. Click on the image to be taken to the video.