Plato 

http://www.iep.utm.edu/plato/

http://en.wikipedia.org/wiki/Allegory_of_the_Cave

http://plato.stanford.edu/entries/plato/

http://plato.stanford.edu/entries/plato-myths/

Heidegger

http://www.iep.utm.edu/heidegge/

http://plato.stanford.edu/entries/heidegger/

http://braungardt.trialectics.com/philosophy/what-is-thinking-heidegger/

Thomas Hobbes

http://www.iep.utm.edu/hobmoral/

http://en.wikipedia.org/wiki/Hobbes

http://braungardt.trialectics.com/philosophy/philosophers/thomas-hobbes/

Rousseau 

http://braungardt.trialectics.com/tag/jean-jacques-rousseau/

http://plato.stanford.edu/entries/rousseau/

John Locke

 Political Philosophy http://www.iep.utm.edu/locke-po/

History of Philosophy, periodization 

http://www.iep.utm.edu/history/

http://en.wikipedia.org/wiki/History_of_philosophy

http://horizons-

2000.org/History%20of%20Western%20Philosophy.html

Ancient Greek Philosophy

 http://www.iep.utm.edu/greekphi/

Political Philosophy

http://plato.stanford.edu/entries/medieval-political/

http://plato.stanford.edu/entries/religion-politics/