Pencil is an animation/drawing software for Mac OS X, Windows, and Linux. It let´s you create traditional hand-drawn animation (cartoon) using both bitmap and vector graphics. Pencil is free and open source.
At the center of the application is a timeline, which allows you to add four types of layers: bitmap image, vector image, sound, and camera. The animation basically works by setting keyframes one each layer and arranging the different layers on top of each other.
Pencil don´t compete with other flash dev software’s or any other animation software, his goal is to create easy and fast 2D traditional animations.
More infos and cooperate with the open source community, please visit http://www.pencil-animation.org/