Internet History Sourcebooks Project
Fordham University: Ancient History Sourcebook: Herodotus Xerxes Invades Greece
Fordham University provides a detailed account of Xerxes plans to invade Greece, the size of his army, his entry into Thrace and the attack on the Athenians.
Other
The Achaemenians
Read about the various kings of the Persian Empire and the battles they created to strengthen their empire.
Other
Bernard Suzanne: Plato's Dialogues: Xerxes, King of Persia
An extensive biography of King Xerxes, including quotes from him and Herodotus and information about his life, death and rule in Persia during 485 to 465 BC.