You can get toothpaste with whitening stuff in it, like any of these:
But some people say they are not so effective.
You can get teeth whitening gels or kits and stuff like that, which sound like they will have more effect. Just search on Google shopping or eBay and you will find some:
To be honest though, like most things in life the more you pay the better
the results. So the best thing you can do if you want white teeth is to
have a whitening procedure done at the dentist.