http://greyscalegorilla.com/blog/2009/10/mograph-2-attractor-project-file-d...
That would work for a still but it's 'jiggly' for an animation, and this
http://www.tools4d.com/?page_id=2143
looks like it would work but your clones would vary in size to fit (I don't have it, I'm only judging on what it looks like it's doing on that page)