I was watching "2012" and I know they used Fume on that show, so I thought I would give the classic "pyroclastic flow" a try. I did this as a sort of afternoon project so the grid wasn't too big. I ran a wavelet on it to get extra detail, but I'm sure I could take it farther with higher settings.
The setup was just a standard fume emitter (box) and just moved forward in the frame. Sim time in total was probably about an hour and a half.
It suffers from the "flicker" but I can deal with that as these are more R&D.