I'm not sure if this one really counts as bonsai but anyway...
It was purchased from a nursery on the South Coast of Australia in 2010. It is a Dwarf Umbrella Tree or Schefflera Arboricola according to its tag.
Sorry about the poor quality of the photo and the shocking angle it is taken from. What is not really clear from the picture is that this is actually attached to the side of a rock with roots trailing down into little pebbles which are then covered with water.