Videotutorial result. Visit www.blendbend.blogspot.com to see how to build this. We're using arrays that follow empties (object offset). The empties are animated by noise applied in the graph editor. Feel free to check my blog (or YouTube channel) for more videotutorials. Two .blend files in the zip. One is the exact videotutorial result and the other is with some added compositing. Enjoy!