number of organizations/volunteers have built http://legislink.org/us,
provides all statutes at large, public law cites, and US code cites from 1787 to present. It also allows for the instantaneous comparison of any two roll call votes since ~1990.
Elie Raad, Richard Chbeir, and Albert Dipanda. Proceedings of the 2010 13th International Conference on Network-Based Information Systems, page 297--304. Washington, DC, USA, IEEE Computer Society, (2010)