Terrific stuff, you can do a lot with OpenCV right out of the box. The Python bindings are pretty poorly documented, though (they change a lot). As much as I'd rather write Python than C++, if you're not already familiar with OpenCV it can be a lot easier to learn with the C++ version. There's a great introduction and API rooted here: http://opencv.willowgarage.com/documentation/cpp/index.html

Shameless self-promotion: If you're interested in face / eye tracking, email me or keep tabs on http://www.gazehawk.com.