ex.fm can detect embedded music files like standard mp3 but also tracks on Bandcamp, Tumblr, Filmbay and Soundcloud pages, although that last one only when on album/track-ages and not the overview-pages.
ex.fm is available as a browser add-on for Safari, Chrome and Firefox. The current version for Chrome is better since it lets you add tracks separately, this not yet possible in the version for Firefox were it adds all the available tracks to your queue (not sure how it works in Safari).
The website itself gives an overview of your profile, trending artists/tracks/music sites and the people you are following. There used to be an option where you could see the tracks you recently found sorted by URL but that option has been removed.
An interesting option is to use ex.fm as one of the online sources of popular music for a genre by using MusicBee.