That is done typing /dance into chat. If you want a lost of all the possibilities, next time you are in game hit F1 to bring up help and in the search box type in "emotes" and hit search. Then click the top link. My favorites are /situps, /pushups, /jumpingjacks, and /playdead.

For a full list of commands, have a look here: http://forums.elderscrollsonline.com/discussion/comment/566677#Comment_566677