I've found a few possible solutions on the Ogre forums, but currently the only usable ones involve a plane.
In one example a person used a simple plane, but to avoid clipping he rotated the plane as the ground changed.
For example when your going up a hill you would need to rotate the plane let's say 45 degrees. In order to prevent it from cutting into the hill.
Another way is to rebuild the blob shadow to match the ground shape, but this way might not be the greatest if you have many active shadows.
One last idea and it might not be blob like enough for you. What about using TextureAdditive shadows and just setting the quality really low to give a blob/pixel look to them?