Wikimedia
Wikipedia: Byzantine Empire
Wikipedia entry on the Byzantine Empire addresses its history, the split with Rome, invasions and migrations from the East, its culture, and the empire's eventual decline and fall.
Boise State University
Boise State University: Byzantine Empire: An Outline
Annotated outline of the history of the Byzantine Empire.
Forum Romanum
Outlines of Roman History: Extinction of the Western Empire: Great Invasions
In this article from the 1901 textbook by William Morey, you read about the split of Rome into East and West. and the invasions of swarms of barbarians.
Other
Royal Academy of Arts: Byzantium: 330 1453 [Pdf]
Gallery guide pairs the history of the Byzantine Empire with the diversity of art produced within its boundaries.
Mocomi & Anibrain Digital Technologies
Mocomi: Sir Dig a Lot: History Mysteries: Rome
Join Sir Dig-a-Lot and Rohan on their brief journey through the history of Rome.
Other
Turizm.net: A Great Empire: The Byzantines
A brief history of the founding of the Eastern Roman Empire, now known as the Byzantine Empire.