Windows Media Player Integration
Notifs. for Song Title - Artist etc. (As done with MusicBee)
Notifs. for current video being played.
Luboš Rückl commented
I did some time ago Snarl extension WMP ( http://sourceforge.net/projects/snarlwmp/?source=directory ).
I know it's not perfect, but nobody did anything better.
In the meantime, before that happens, at least you can use mine.