Quickcast.io is a free open source Mac app that lets you create 3 minute screencasts videos.
Simply download, install, click the QuickCast logo in your toolbar and hit record. After a 5 second count down you’ll be screencasting away. The Quickcast icon will give you an idea of how long you have left.
One nifty little feature is that if you record a screencast of under 10 secs and under 300px height/width, you can retrieve an animated gif (example here) as opposed to a full blown video.
Here’s a quick example of a Quickcast Screencast in action: