The Article V Library:

This is a cool research site–The Article V Library.  Robert Biggerstaff has collected volumes of materials not just on enacted constitutional amendments but proposed constitutional amendments through the years, including state calls for constitutional conventions.  He also tracks states that have rescinded previous calls for conventions.

This is quite and exhaustive program that could prove a fruitful site for researchers.  I think he is looking for feedback any needed corrections so please check it out if you are interested.