Just in case you have not seen this short animation, here it is. This has been a very popular animation not only because of the dedication of all the artist that participated in the creation but also because it was created with an open source program (free) called Blender.
For those of you that do not know, Blender is a free open source 3D content creation suite available for all major operating systems under the GNU General Public License.
More information about Big Buck Bunny can be found here.