http://www.remixofthecentury.com/
Remix of the Century is a Music Hackday project by @tomhannen, @indeox, and @hpettersson which aims to explore a century (roughly) of Billboard charts using data from the Whitburn Project.
The Echo Nest API is used to augument the chart data with per song audio characteristics like tempo, mode, and key as well as some Echo Nest specific metrics like Danceability and Energy.
The Echo Nest Remix API is used to create one long beat matched remix of all highest ranked songs we could find audio for.