The Basics: How are the statues chosen? Who decides? What are the rules? How are statues replaced? We’ve got the answers here.
The National Statuary Hall Collection (external link): The list of statues from the Architect of the Capitol.
The Origin of the Collection (external link): The history of the Collection from the Architect of the Capitol, along with links to the forms (pdfs) for replacing a statue.
List of Statues by State (external link): This is the list provided by the Office of the Clerk of the U.S. House of Representatives. The organization of this site is a little more user-friendly than the material on the Architect of the Capitol site.
History of Statuary Hall (external link): Also from the Office of the Clerk, this is the history of Statuary Hall. The site also features The Splendid Hall, a virtual tour of the Old House Chamber (now Statuary Hall).