Is there a way to queue up the next song on my iPhone? Is there a way to pick which song should play after the current song finishes? 

I often browse my music library while listening, and I'll want to play a specific song, but not stop the current song in the middle. Is there a way to queue up a song to start after the current one?
As they say in the iPhone world, "There's an app for that" (Review) :-) It's called OnCue.