Usually when it comes to vectoring, Adobe Illustrator is the first choice but for me, Adobe Flash comes first in mind :D
Here's the simple tutorial on how to vector a sports car.
Download the Car photo here : http://the-pit-monsterstock.deviantart.com/art/Car-stock-29-59811242
Open Adobe Flash and go to File> Import> Import to stage. Locate the saved car photo and click OK.
We need to make the photo look transparent for easier tracing later on. To do this, click on the photo and press F8. Choose the graphic option and click OK.
Select the photo and on the properties bar (Ctrl-F3), change the Color bar to Alpha. Set the opacity to 38% - 50%.
You can now use the pencil or pen tool to start draw the outline of the car. You might want to set the "Smoothing" to 60 and the option part (below the tools) to "Smooth" for better tracing :)
Once you've done with the outline, it's time to color the car. Use the paint bucket tool to fill in the color you prefer. You can even use the gradient colors!
Remove the photo layer and you're done! Try export the image to JPG or any other format for various usage.
The Vector Car fla available for download, here - http://www.ramesstudio.com/adobetuts/car-vector.fla
Thanks and hope its useful for you.