There is a ton of information out there on the web, but books are far more trustworthy. The discussion about female gladiators is quite interesting; for decades no one wanted to accept the possibility that women could fight. At any rate, it seems that gladiatrices were actually more common on the fringes of the Empire than in Rome.

There is a new book out about gladiators in Pompeii (remember that the amphitheater there is the first one in the world, predating the one in Rome by about 150 years). Here's the new title: Luciana Jacobelli, Gladiators at Pompeii, (L'Erma di Bretschneider 2003).

This book tends toward the melodramatic, but is factual and an easy read for non-scholars: Alan Baker, The Gladiator: The Secret History of Rome's Warrior Slaves (Da Capo Press 2002).

Michael Grant's Gladiators is the sort of scholarly and dry handbook that most people have read. It's a tiny bit out of date, but I'm sure you'll find it helpful. Chapter 3 is all about the different kinds of gladiators (there were four basic types), the fighting techniques, weapons and armor.

There is currently an exhibition of Gladiator's tombstones at the Ephesos Museum in Selcuk, Turkey. You might be able to locate a copy of the exhibition catalogue, but it's only available in German or Turkish - last time I checked, anyway.