you could do like a "set the scene", and take ur class back in time...describe the surroundings, even make up a role play perhaps? get your audience involved. They learn more and so will you! You could make up a story about a dual kingship in Sparta that incorporates your knowledge of the topic, and it is also an interesting way to get the message across to your class mates.
You could do a game show type, where your the host and you pick 3-6 contestants. You firstly give them the information and then quiz them after. Bribery such as chocolate always works
You could divide the class into 2 teams...they can get REALLY competitive sometimes! Even if you aren't going to award them with a prize, just them knowing that they bet the other side is enough satisfaction!
lol
Hope that helps