The Constitution of the United States
From the National Archives and Records Administration comes this online exhibit on the Constitutional Convention of 1787. The site features a Founding Fathers page, which contains the biographies and portraits of each of the 39 delegates who signed the Convention. You can also look at the actual pages of the Constitution online, read A More Perfect Union, an article that takes an in-depth look at the Convention and the ratification process, and access questions and answers related to the Constitution.
http://www.archives.gov/national-archives-experience/charters/constitution.html
The Constitution of the United States
This page is part of the “Archiving Early America” project, a collection of primary source documents from 18th century America. The site features the Constitution and includes an explanatory passage, full text of the document, and high-resolution images of the original document.
http://earlyamerica.com/earlyamerica/freedom/constitution/index.html
To Form a More Perfect Union
This site is part of the Library of Congress' “American Memory” online exhibit, and features the development of the United States government. This site contains historical documents, engravings, and brief essays on the critical issues related to formation of the government.
http://lcweb2.loc.gov/ammem/bdsds/constit.html