Rick Moquin
Omono
Catlitter (also jokingly known as 'Kittydama') or Diatomaceous Earth or 'Diatomite' For anyone living in the UK, I would wholeheartedly recommend 'Tescos Premium Lightweight Cat litter'. This fired clay has excellent properties as a bonsai soil.
I have been using this 'soil' for all of my trees for a number of years now and would not switch to anything else. It is very cheap and given that almost everyone in the UK lives within 5 miles of a Tesco Supermarket, it is easily obtainable.
For more information about inorganic soils, sorces for these soils around the world, please see this article Cat Litter as Bonsai Soil
... as a matter of fact Harry has a complete listing for varius countries contributed and udpdated to his site by various members of the net.