This is a feature that i am missing both in itunes and on the ipod...
basically it's just a queue for which song to play next...
once the song has played it's out of the queue and the next song in queue is played..
kinda like a dynamic playlist
only alternative now is playlists (which isn't very userfriendly..), random play (which might play unwanted songs), or manually selecting each song every time (which is a pain in the @ss)...
just enter party mode and a splitscreen (for itunes) will tell you which songs are in the queue double-clicking will add to the queue, the gui for the iPod has to be thought trough a bit but it should work great!
/speedy