The era between 27 BC under the rule of Augustus, until Rome fell in 476 AD, is usually referred to as the Roman Empire.
Regular Websites
Illustrated History of the Roman Empire
This vast website centers on the history of the Roman Empire, with sections focused on the founding, the early republic, the late republic, the apex, the decline, the collapse, and the culture of that society. - Illustrated History of the Roman Empire
http://www.roman-empire.net/
Presents biographical profiles of relevant people in the Roman Empire, including Aurelius, the Caesars, Brutus, and Claudius as well as magistracies, and other pertinent topics. - Livius: Roman Empire
http://www.livius.org/rome.html
The Philosophies and Religions of the Roman Empire
Begins with the founding of Rome and proceeds through neo-platonism, Roman mythology, Christianity, and gnosticism. Takes the reader through the incidents which led up to the fall of Rome and the rise of Islam. - The Philosophies and Religions of the Roman Empire
http://webspace.ship.edu/cgboer/romanempire.html
This website provides an illustrated history of the Roman Empire where you can learn about the Republic and Empire of Rome, one of the most important civilizations of the ancient world. You can also find reenactors who have recreated various aspects of Roman society including the army. The website also has a timeline of Roman emperors. - The Roman Empire
http://www.roman-empire.net
Devoted to the Roman Empire, this site shares information about the economy, government, culture, and military and provides maps and a timeline, as well as details about enemy leaders. - UNRV History: Roman Empire
http://www.unrv.com/empire.php