Instead of tootpaste, brush your teeth with baking powder ^.^ Just mix it with water to make it into a paste and your teeth will be sparkly white in no time haha :D

Check out these methods..I used the strawberries trick several times and it did work out nicely....

http://www.becomegorgeous.com/body-and-skin/top_to_toe/natural_teeth_whitening_remedies-4092.html

http://www.becomegorgeous.com/body-and-skin/top_to_toe/best_home_teeth_whiteners-2849.html

I think you can wash your teeth once a week with baking soda...I used this method several times....

Try mixing one part lemon juice with two parts baking soda. It'll bubble up at first, so don't freak out! ;) after you mix these two ingredients up, use your finger to scoop up the mixture and put it on your teeth. Leave for as much time as you have (yet I would say no more than 30 minutes..), then spit it out and brush your teeth!

The taste is.. um.. Not so great, but you'll get used to it! It's worth it for the results!

You could also try rinsing your mouth with peroxide once a day.