If you aren't already signed up with SaveMore -- sign up now! When you sign up you get a $10 credit that can be used toward your first purchase.
Today they have a Tooth Whitening Pen for only $8.50 (including shipping!) = FREE after your credit. You will see it as the side deal here.
If you already got and used your $10 credit, you can easily still get this free just by telling a friend with your personal referral link, when they get their free tooth whitening pen, you get another $10 credit! :)