I've been trying to use the Simpsonize Me generator at http://simpsonizeme.com for a few days now but its been slammed. Finally, using IE, I was able to get it to work. You upload your pic and it fits your features into a Simpsons-like character.
Based off this pic
They returned this image
Its quite finicky... it wants a large picture of just your face. No black and white, no shadows, looking directly at the camera. It was hard to find one that met all the criteria.
Overall though, not a terrible reproduction!