If you like visual demonstrations of ML topics, you may be interested in http://ponder.hepburnave.com. It is an interactive demonstration of a self-organizing map, generating a 2D-map from a spreadsheet with multivariate data. It's an unsupervised learning approach, good for data exploration tasks, less so for classification tasks (/shamelessPlug).

It's the classical exploration vs exploitation tradeoff. What do you do, try a radical new variation or fine tune this one?