Nate Smith is a wedding & portrait photographer in Salem, Oregon who has a fantastic blog full of Aperture 3 tutorials and videos. He just posted a new video to his website showing a simple process for teeth and eye whitening in Aperture 3.
Check out the tutorial on his site, and make sure you add him to your Google Reader account or bookmark his website.
Teeth and Eye Whitening in Aperture 3 via Nate Smith