You can buy whitening kits from chemists. I'm not sure how well they work. The best method so fat is zoom whitening, but that has to be done by a dentist and it has varying results.
chazza - i thought that was just because your gums became more red so your teeth seem whiter? I use pearl drops tooth paste and it makes teeth a bit whiter but not what you would achieve from dentist.
Sonak I read an article in Look Magazine some six months ago about teeth whitening kits you do at home and would never do one after reading that. Some went wrong and the people end up with really sensitive teeth and problems.
Mix a little bit of baking soda in with your toothpaste. Don't do it too often, as it will wear down the enamel and harm your teeth. Your teeth will be a little sensitive to cold afterwards, but it works.