Recently I created a demo video to show off a new feature in Blender 2.65 - Collision objects now cause vorticity when passing through smoke!
This effect is something that the Blender smoke simulation was lacking for years now, but very important when you got moving collision objects because in the real world they would make the smoke swirl. Check out this example, on the left the new simulation in Blender 2.65 and on the right the old behavior:
The scene basically consists of a static field of smoke through which the logo is passing. Thanks to the new vorticity from moving objects the left version looks much more natural.