Nice link on the battle:
http://www.answers.com/topic/300-spartans
Jon, its my understanding that the Greek Hoplite wore a full armor back then. Armed with a large shield an 8 foot spear and short thrusting sword. So the half naked guys would have been an invention of Frank Miller.
I think the hoplite and the phalanx are considered the prototype for the roman legion.
What I thought was neat is that some of the quotes from the movie are actually attributed to the historical spartans.
"Then we shall fight in the shade"
"come and take them(our weapons)"