I've used Crest whitestrips and gotten good results. They also have a whitestrips pro
that is stronger that I've used. I've also used Crest Night Effects
which I really liked because you paint it on your teeth at night and sleep while they whiten.
As you can see I'm a bit of a teeth whitening junkie, its pretty dangerous. People comment on how white my teeth are but I always want them whiter. Have you ever seen that episode of Friends when Ross whitens his teeth and they glow in the black light? That's what I aim for.
But seriously I've had to stop for the past year because its not good if you do it too much.