Daniel Lemire finds recommendation systems (I can't bring myself to call them "recommender systems", since they seem to me to be targeted more at recommendees) fascinating, though he is less than impressed by their implementation, such as Google's pagerank. Personally, I don't need sources of more information; I need lower volume and greater signal-to-noise ratio. A system that recommends that I not read something -- now that would be valuable (perhaps you're thinking the same thing right about now).
But he's right about one thing: Google's chart API is the rebirth of GNUplot. Except that it's not really open source. Anyone want to write a MATLAB function to export a graph as a Google chart?