After the Peloponnesian War - Thirty Tyrants Replaced Democracy with Oligarchic Rule in Athens: The treaty between Athens and Sparta at the end of the Peloponnesian War and its aftermath. [About.com]
Ancient Greece: The Pelopponesian War: Richard Hooker's module on the history of the sequence of events and alliances in the Peloponnesian War.
Histories: English translation of Thucydides' History of the Peloponnesian War [Perseus]. Three versions in Greek also available.
HWC, The Peloponnesian War: Dr. Ellis L. Knox breaks up the history of the war into 17 chapters, with suggestions for further reading.
Peloponnesian War: English translation by Richard Crawley [ICA].
Peloponnesian War Timeline [About.com]: Timeline of the treaties and fighting among the Greek city-states in the Peloponnesian War.