I thought I'd refresh this thread to see if anyone has more to add -- perhaps songs written since the thread was first posted.
Some that seemed to me to be relevant to the category (in addition to The Midnight Choir and Hard Times Come Again No More and Nobody Knows You ...) are
Trudy -David Maloney
There But For Fortune - Phil Ochs
Will There Be any Boxcars In Heaven - Jimmie Rodgers
Pretty Papers -- Willie Nelson
Here Comes That Rainbow Again -- Kris Kristofferson