I have this one which has a dual USB and also available at Best Buy for the same exact price and is the same exact size as the Belkin because I often have a passenger who also needs to charge their phone/mp3 and I just find it more convient to have two USB ports
Griffin Technology - PowerJolt Car Charger
Also, if you search on the web, you can find it for $9 versus the $24 that Best Buy wants for it.