John Tropea has an amazing ability to keep in his head (and subsequently on his posts) a big map of all the related tools and applications that are remotely related to any given topic.
As a result of his encyclopedic knowledge of all things RSS/Attention/Recommendation, he has written a lengthy post about various applications of APML in every day web 2.0 tools.
He has a fantastic view of an APML enabled world that puts the user at the center of their Attention driven experience.
In "APML", "Media 2.0", "collaborative filtering", "collaborative recommendation", "johntropea", "recommendation engine", "web 2.0"