I've been using this awesome website, Taaz.com, for a while now so I figured I'd pass along the fabulousness to my lovely readers!
Basically, the site allows you to upload any photo of yourself and add makeup, whiten your teeth, and even try out different hair styles! You can actually even try out complete celeb looks to see how it would look on you.
The coolest part, in my mind, is that the makeup you choose is actual makeup. The site tells you what product you're using so that if you like the way a certain color looks on you, you can run out a buy it. It's super helpful for when you don't feel like trying out a million different eyeshadows at a makeup counter, but still want a new look.
The result is a fairly natural-looking picture with whatever products you picked over it. That said, you can also get crazy and creative with it if you want. It's totally up to you. I can literally spend hours trying different makeup on my "face".
I also have to admit that I love using the site to touch up some of my own pictures (like adding a little mascara and blush to a pic that makes me look washed out).
It's really a great resource, and best of all it's free! Huzzah!