There are countless links to Internet websites about the US Constitution, ranging (among many others) from a lengthy wikipedia article, to the National Constitution Center's page of educational resources, to cartoons about the constitution, and the Library of Congress' page.
The US government recently
announced its 10th edition of the now nearly 3000 page
of the United States of America: Analysis and Interpretation",
a comprehensive analytic legal treatise prepared by the order of the
US Senate. It includes not only the text of the US Constitution, but
also a clause-by-clause discussion of the document and a discussion
of all US Supreme Court cases relevant to the interpretation of the
Constitution. The text is also available as an app
for I-devices and is being developed for the Android platform.