An interesting bit of additional info on "Bonnie Blue Flag":
While it was written by McCarthy, he didn't complete it until all the dust had settled with secession which didn't occur for several months after South Carolina went out. He premiered the first version of the song at the celebration in Jackson, MS when the vote to secede had been taken. In the version sung today, there's a glaring error that most Mississippians interested in local/state history know, that being that Mississippi was the second state to secede not the third. Mississippi preceded Alabama by a slight amount of time. When I occasionally do the song, it is usually for Mississippians so I change the order of the states to put Mississippi in the right place.
Otherwise...where's Jed Marum in this thread? A lot of his career has been built around the war both original war period songs and new stuff he's written (some of which is better than original period songs in my opinion). One of my top favorites is "Monaghan's Lament".