Pivot is a free stick figure animation software to create simple stick figure animations. This free Stickfigure animator lets you easily create stick figure animations of all type. You just need to define your stick figure, and then you can define different frames of your scene.
Pivot comes with a simple to use interface, and provides basic animation features. To make it easy to create your stick figure animation, Pivot uses the concepts of fixed length sticks, so that your animation stays consistent from frame to frame.
Pivot also comes with a stick figure builder that you can use to quickly create your stick figures.
Here is a simple animation created with Pivot Stick figure animator:
Pivot Stickfigure animator is extremely easy to use, but it also lacks proper documentation. However, there are lot of video tutorials around to learn Pivot.
Download Pivot Stickfigure animator here. As per Wikipedia, this project is now defunct, and no new versions are being released. But the version that is currently out there is itself good enough for simple animations.