purple smoke
This animation was created by accident. I played with the new smoke/fire material of the object/Quick Smoke menu in blender 2.72-RC and accidentally set one of the parameters to -2. I have no idea how or why this works but its definitely worth exploring further.
you can download the blend file here
See also:
smoke density selection
cycles ink drop
reverse smoke
dissolving smoke
Texture forcefield experiment 10 - smoke curl
cycles ink drop
reverse smoke
dissolving smoke
Texture forcefield experiment 10 - smoke curl