Big Buck Bunny is an impressive showcase of Blender, the open source 3D software. The character design and animation is top notch. The story this time is much simpler than their previous clip, Elephants Dream (embedded below).
This short clip is also available for download in HD format at their Big Buck Bunny official blog. 1920 by 1080!! Make sure your graphics card is up for the job.
They are doing some really great web promotion by releasing the clip for free, and putting it on Youtube.