Free Vector-based 2D animation software for Mac, Windows and Linux - Synfig

Synfig is a Free, powerful, industrial-strength vector-based 2D animation software package, designed from the scratch for producing feature-film quality animation with fewer people and resources. While there are many other programs currently on the market to aid with the efficient production of 2D animation, we are currently unaware of any other software that can do what our software can. 2D Animation has traditionally been very expensive because every frame must be drawn by hand. Even with today's digital inking and painting software, the process still relies on individuals hand-drawing each frame. This laborious task is called "tweening". Its animation technology eliminates the task of manual tweening, producing smooth, fluid motion without the animator having to draw out each frame individually. This allows you to produce 2D animation with fewer people while producing a product of a higher quality. Link: synfig.org