Some Atlanta based movie car rental sites:

Precision Drivers Atlanta:
http://www.precisiondriversatlanta.com/index.html

Atlanta Picture Cars:
http://www.atlantapicturecars.com/home.html

Picture Cars of Atlanta (no listings, just general site):
http://picturecarsofatlanta.com/home

Southern Picture Cars:
http://southernpicturecars.com/