A powerful way to sell your used car is to create a simple video "walkaround" of your vehicle. It's what car salesmen do with potential buyers: walk them around a vehicle as they point out various features and options. You then post your video on YouTube, a site that's visited by millions of viewers each day.
Now that most digital cameras can record video, and you have a free, heavily trafficked place to upload videos, it makes sense to have a video ad in addition to an online classified. Put the video link in the classified ad and the classified link in the video to reach different types of buyers.