Cliff note-type summaries
Reading, writing and researching history: a guide for college students
A friendly site from Columbia University of The Mongols in World History
HyperHistory World History
Te Ara – The Encyclopedia of New Zealand is a comprehensive guide to our peoples, natural environment, history, culture, economy and society.
The University of Tufts Classics Dept hosts Perseus, a "digital library of resources for studying the ancient world. The library's materials include ancient texts and translations, philological tools, maps, extensively illustrated art catalogs, and secondary essays on topics like vase painting."
Get an overview of Roman history through 40 maps
DIR is an on-line encyclopedia on the rulers of the Roman empire from Augustus (27 BC-AD 14) to Constantine XI Palaeologus (1449-1453).
The Research Archives of the Oriental Institute in Chicago offer a guide to Internet resources on the ancient Near East
At a less academic level, if you want to know more about Egypt, Eternal Egypt is a good place to start
Described (by others) as the standard starting place for Medieval studies on the Web, the Labyrinth is sponsored by Georgetown University. Make sure you use the new Labyrinth when searching!
The Online Reference for Medieval Studies is put out by academics for fellow academics and serious students.
Students of Britain during the Renaissance period can also find resources on Perseus (see above).