I heard that brushing your teeth as soon as you can after drinking coffee is a good way to prevent staining. Not even necessarily using a special type of toothpaste, but just brushing as quickly as possible after having it so that the coffee doesn't have a chance to stay on your teeth long.

It's kind of hard to do when you're out at school/work during the day, but I have heard of people carrying a small toothbrush/bottle of toothpaste with them when they go out if they're really concerned about it. ^__^