Get settings from the site Weecho gave us
Under Shadows Tab-
*Select Depth Map Shadows
*Resolution: 1024
*Filter size: 5
*Disk Mapped Dmaps: overwrite existing dmap(s)
Under Mental Ray tab-
*Use mental ray shadow map overrides
*take settings from Maya
*play with softness
You can also use the linear decay rate to soften the shadow over time