Appalachian clogging

Morris dancing / Molly dancing. Definitely energetic (leaping), crazy (swinging sticks around), and interesting (English countryside fertility ritual).

Irish step dancing and Scottish Highland dancing are energetic, and most dances have a historical reference, but they are highly technical and cause shinsplints until you're well- and frequently-trained (and even then), so I wouldn't recommend them for a fun class.

Let us know what you decide on! What else are you thinking of?

How about belly dancing?