The Pre-Socratics and the Sophists
A romp through the history of philosophy from the Pre-Socratics to the present day (Oxford University Department of Continuing Education)
The Sophists and Socrates (Thought Academy)
Stanford Encyclopedia of Philosophy: Sophists
http://plato.stanford.edu/entries/sophists/
Internet Encyclopedia of Philosophy: Sophists
http://www.iep.utm.edu/sophists/
Internet Encyclopedia of Philosophy: Presocratics