This past Saturday was the 2012 New Times/TimesOpen Hack Day hackathon where Beau Lebens, a programmer for Automattic, received an honorable mention for Readtrack, an experimental tool that gives music recommendations based on the content you’re looking at. According to Lebens, "It’s a bookmarklet-powered little app that analyzes the page you’re looking at (using the AlchemyAPI) and then tries to find related music (using the EchoNest API) which it then plays back to your in your browser (using rdio)."
AlchemyAPI's Concept Tagging analyzes the page content and then provides a list of keywords and content recommendation that relates to the concepts represented there. The top 2 concepts are passed to EchoNest's Song search API to find songs that match. Then those tracks are loaded and played via a jQuery-powered web-player using rdio's Web Playback API.
Here's the full description of the WebApp: Readtrack.