This is the best kit I've seen yet. It comes with custom trays, the little LED light and something that boosts your enamel to make your teeth stronger. I've tried two different ones so far from other deals and companies and my teeth are whiter, but not where I want them yet so I bought this one, too.
http://www.eversave.com/dallas/kissme-teeth-whitening-2?sourceid=60585&sdversion=13717_AThis is a referral link.