iwilltry has posted a tutorial showing how to measure your drag coefficient and coefficient of rolling resistance. The purpose of this is to allow someone to measure changes they have made to the body to either reduce or if you happen to increase drag. Another commenter makes a point of using a video camera and recording the coastdowns on your speedometer. Then digitizing it so you can go frame by frame and measure the difference in time and speed.
These tips are mentioned on instructables.com for the use of reducing drag to help with gas milage. I see it being a neat tool for helpful for those who enjoy the drag strip. Reducing the extra bit of resistance might help someone.