"Cindy's Crying" by Tom Paxton is one of my favorites, very poignant.
I can't remember all the words off the top of my head, but the first verse:
   Cindy's crying but it ain't no use
   She's got a habit she can't turn loose
   She's started (grabbing?) every man she meets
   She's gonna be a hooker down on Bleeker Street....

Good tune; makes the connection between prostitution and addiction.