Other
Salariya Book Company: You Wouldn't Want to Be a Roman Gladiator!
A web-book designed to show the pitfalls of being a Roman Gladiator. Although this is a cartoon book, it does give you some elementary knowledge about the Roman Empire.
Vroma Project
V Roma Project: Spartacus: Historical Background
Contains a good chronology of the slave rebellion led by Spartacus. This page was created by Barbara F. McManus of The College of New Rochelle.
Able Media
Classics Technology Center: The Roman Gladiator
Nice overview of the history of gladiatorial games and their function in Roman society. Mentions how people became gladiators, how they trained, and the possibility of female gladiators.
Stephen Byrne
History for Kids: Ancient Roman Families
History written for elementary students to learn about families of ancient Rome and how they were structured. Students can get a sense of the relationship between family members, including slaves and elders.
Other
United Nations of Roma Victrix: Roman Gladiator
An account that describes who the gladiators were, how they fought and why, how were they trained, and more. It also provides some interesting facts about them such as that there were women gladiators.