Check out Tracy Performance. I have one for my Mustang and one for the Cobra. My buddy has one for his Mustang, Roadrunner & Camaro. They offer several different types depending on what you want or need. The best thing about them is the fit and the fact that they are floor length, so dust can't swirl up onto the paint.
http://www.carcovers.com/general_info.html
Andrei