Be very careful about what you buy to lighten your skin! I have recently purchased a book about skin of colour (as in any skin that is not white). It is written by a bunch of doctors and it warns that there are many companies out there who know we non-whites get dark blotches on our skin and are out to take advantage. Also, many products in the West are designed purely for white skin, meaning they may actually make non-white skin worse instead of improving it!
Here are the recommended creams for dark blotches from the book: Ambi Discolouration Fade Cream, Palmer's Skin Success, Esoterica, Porcelana and Skin Salon Gold. All of these products contain 2% hydroquinone. Do not buy a product that contains more than 2% as high amounts of this stuff can be dangerous, which is why it has been banned in some countries. Very high amounts have been shown to cause cancer, so be very careful and only apply a tiny amount to the blotches once or twice a day.
Alpha and beta hydroxy acid products also help to fade dark blotches: Alpha Hydrox, Avon Anew and Skin Salon Gold.