"Semi-Shuffle" for iTunes and iPod

I would love to have a plugin for iTunes that allowed me to create "suggestions", "connections" or "musical journeys".

Would work like this: after song A, I would normally (or often) like to listen to song C and sometimes to song F. So in iTunes, I drag a line from A to C and another one from A to F and I tell iTunes to use these when shuffling, one or the other.

Thing is: I think stars and playlists are fine but they do not come close to capturing the way I listen to music. There is no "mood" in there. No concept of memories attached to songs and the string of memories in my head. So we need more!

This being 2009, I would probably also want a way of importing those "connections" or "musical journeys" via social networks like last.fm, facebook or whatever else I am using.