Here are some good internet sources for political philosophy, especially classical works:
Many books can be accessed through:
http://digital.library.upenn.edu/books/
You can search here for books either by the title or the author. I couldn't find either Rousseau'sSocial Contract or Hegel's Philosophy of Right, but it is worth a try. There is apparently no mechanismforsearching the texts themselves.
The Internet Classics Archive contains works by many classical Greek and Roman thinkers. It can be found at:
http://classics.mit.edu/
A site that has some texts but with some broken links is provided by Mason
West as "The Master Works of Western Civilization"
http://mason-west.com/MasterWorks/index.shtml
A number of sources, including Aristotle, can be accessed through:
http://www.ipl.org/cgi-bin/ref/ref.out.pl?ty=long&id=law30.40.60
If you should find other useful sources please let me know.