US Navy
Naval Historical Center: The h.l. Hunley in Historical Context
An extensive history of the Confederate submarine, H.L.Hunley, the first submarine to sink a warship. Also information about two earlier prototypes.
Other
On Deck: Submarines in the Civil War
The Hunley wasn't the only submarine used in the Civil War. Read this comprehensive look at the research into underwater warfare and the results of that research.
University of Houston
University of Houston: Engines of Our Ingenuity: No. 381: Civil War Submarine
A short discussion about the invention of the submarine and its use by both the Confederates and the Federals in the Civil War. This is a transcript of an accompanying radio broadcast.