Caramelldansen is a meme combining a Swedish song of the same name with a very simple dance. The dance originated in Japan, where it's also called ウマウマダンス (uma uma dance) / ウッーウッーウマウマ (ua- ua- uma uma) due to confusion about the lyrics. I like the Chinese names for it. In addition to 焦糖舞 (caramel dance), they call it 兔耳舞, which means Rabbit Ear Dance. That's a pretty good description of the dance. People will release videos of their favorite anime characters doing the Caramelldansen dance.
Anyway, there are literally thousands of variations you can find on Youtube or Nico Nico Douga. I'm going to list my top ten favorites. (top 10s are good, right?) My favorites are mostly videos that are either themed or have large amounts of characters. As far as I care, this list is the best of the best. Well, except for the one I think is the absolute coolest, which I'll save for tomorrow's post.
3D-CG Vocaloid Nendroids
One Piece (cast up to 2010)
Full Metal Alchemist
Evangelion (there's also a second part if you click this link)
Yu Yu Hakusho
Lotsa Random Characters