Forum Romanum
Outlines of Roman History: Beginnings of Rome: Traditions of the Early Kings
This chapter in William Morey's textbook on Roman history describes the legendary founding of Rome and the reign of the early kings.
Yale University
Avalon Project at Yale Law School: Laws of the Kings, 753 510 Bc
An comprehensive listing of the Laws of the Kings, the laws set down by the seven kings of Rome during the monarchy.