Pencil is a very cool open source animation/drawing application that lets you easily create stunning animations. The software supports both vector and raster layers and exports in a variety of formats. It’s still a little rough around the edges but makes up for it with a super easy interface. Pencil runs on both Mac and Windows platforms.
You can see my first attempt at Pencil here.
Pencil is not intended to mimick web-oriented vector-based animation software such as Flash. Its main purpose is to make traditional animation. Neither does it try to rival commercial software targetting the professional animation sector. Pencil is intended to be a simple program enabling anyone to make 2D animation.