Carsten said:
Very cool!
There are many cartoon animation programs available that offer free trial downloads. Here are three cartoon animation programs that are completely open-source, which means they are free for you to use. Though they vary in complexity, ease of use and features you will likely find one that best suits your animation needs.

Pencil Homepage | Download Pencil
Kudos to Mr. M for pointing this one out. Pencil is an interesting application in that it allows for both vector and bitmap drawings. It’s as if the drawing tools of Photoshop were combined with the powers of Flash. The application itself has been pared down to its most essential elements, meaning it’s an excellent introductory animation software package.

Synfig Homepage | Download Synfig
The creators of Synfig have ambitious goals of their software being used to create feature film quality animation. After watching an impressive demo it looks like they’re not far away from their goal. Synfig can create complicated lighting and camera effects, it’s up to you, the animator, to use them properly.
As of this writing, there is no Mac version due to technical issues.

CreaToon Homepage | Download CreaToon
Another PC-only animation program, CreaToon uses a cut-out animation
process, similar to Toon Boom. The application itself seems a bit less
polished, but the ability to use bitmap images within the program is
useful. Note: CreaToon is Freeware
