This question fits my definition of trivial. If you copy the question and paste it into google, three of the top five responses answer the question.
- One mentions the Hoplites
- I'll grant you that Yahoo answers answer is as sparse as the movie's armor.
- Roman Army Talk cites (unreliably) an interesting counterexample
The best answer is the first, from History vs Hollywood.
Did the Spartans really fight with virtually no body armor?
No. The movie 300 has the Spartan soldiers fighting nearly naked without any form of body armor protecting them. Body armor was a valuable asset to the real Spartan soldiers. 300 author Frank Miller commented on this alteration in an Entertainment Weekly interview, "I took those chest plates and leather skirts off of them for a reason. I wanted these guys to move and I wanted 'em to look good. ... Spartans, in full regalia, were almost indistinguishable except at a very close angle."
Clear, concise, and it even provides a picture of spartan armor. And an authoritative quote from Mr. Miller which ought to settle the question of why the movie portrayed them that way.