An H2O playlist is a shared list of readings and other content about a topic of intellectual interest.  it is a simple yet powerful way to group and exchange useful links to information -- online and offline.

I saw a presentation at Educause about this and talked to these guys.  It is an open source project in java/tomcat.  Really very similar to TagIt, but it is presented in the context playlists.  Also, cool idea of 'influence' rather than subjective ratings like in TagIt...