Find Faces
Facial recognition is an obvious and important application of machine learning. In machine learning, we take tagged input data and write a model that maps the input to output that looks like the tags. We then try to minimize the distance from the input to the known tags. In the process, the mathematics of probability theory, linear algebra, and calculus all play a fundamental role.
Here's a toy example that finds faces in an image and takes you on a tour of those faces. There are three built in examples and you can also upload your own image.
It does take bit of time to load, though.