Most litterers know they are litterers, but I wonder whether some of the people who get reported to your site might be clueless about other options. Cars these days don't always have ashtrays, so what IS a person supposed to do? Maybe you could ask state governments to send message to offenders (if letters are still sent?). Link to vendor, or just a page of photographs? Here are some:
http://www.epinions.com/t-smokeless-ashtrays.