Undoubtedly, Blender is one of the most popular tools for creating 3D animations due to the fact that it is free, cross-platform software with GPL license. Thirteen years after the Blender Foundation distributed it freely (after having been developed previously by a Dutch animation studio), there have been many updates and improvements made to the packet. Now, with the recent launch of its version 2.67, the ability to create 2D animations from 3D projects has been included, among other features.
The so-called Freestyle engine is a non-photorealistic rendering system that allows you to create 2D effects from a 3D animation created with Blender. You can later apply all kinds of effects that help you achieve results similar to those of the original drawing, such as is the case with the popular system Cell Shading, and other resources pertaining to more experimental animation. The following video is an example created with Blender.
Also, several features have been added to this version, such as improved brushes, a new shader for creating rough and textured surfaces, improved node editing, tools for 3D printing, and several minor changes that you can see on the official Wiki.
Official Website | http://www.blender.org/