You mean those soft shadows dropped right under the object?
http://www.smcars.net/forums/attachm...g?d=1150315755
http://www.smcars.net/forums/work-pr...were-rims.html
http://img92.imageshack.us/img92/231...07400004jx.jpg
http://www.smcars.net/forums/work-pr...diablo-sv.html
If those examples show what you mean (and thanks to the people who posted those WIP's

) here's how they can be done quick and dirty
Under lights creation tap, select skylight, make on in your scene.
Press F10 (render dialog) and under the advanced lighting tap, press the drop down box, and select "Light Tracer". Now you're ready to render

Just remember not to have more lights than that one unless you want to make some tweaking. If you render now, you should get the soft shadows