How high-res is the mesh for the ground?
If its fairly low res, just use a flat black object slightly above the ground under the charecter.
If its fiarly high res, have a negative spot light point at the charecter and adjust its size till you get a "black blob" as a shadow.
The second method works cool because the shadow goes up walls and stuff...but as the lighting effect only falls off from the vertexs its quality depends on mesh resolution.
"The man who says it cannot be done is generally interrupted by someone doing it." ~ Elbert Hubbard