The American Presidency Project
This website contains a searchable database of tens of thousands of documents from U.S. presidents from 1789 to the present. Includes inaugural addresses, press briefings, signing statements, and debates.
Also features data on topics such as popularity and number of public appearances, election results back to 1828, and an archive of audio and video clips. A collaboration between John Woolley and Gerhard Peters at the University of California, Santa Barbara.
URL: http://www.presidency.ucsb.edu