One of the best and most fun workouts you can get dancing is from contra dancing. Many people have never heard of this, but it is an old American dance style from New England, originally from England, by way of France. Square dancing comes from contra dancing. The types of people you will meet square or contra dancing may be vastly different, but you get an idea of the dance style.
Each dance is taught and prompted by a caller. You dance with a partner, in a long line with other couples. Thoughout an evening you may do a dozen or more dances, and each may last 10 - 15 minutes. Dances are mainly a set of simple figures strung together done to a fast walking pace, and repeated as you travel up and down the line and interact with the other couples. You will almost always dance to live music--fiddles, guitars, pianos, mandolins, and countless other instruments.
One of the things that makes this type of activity so much fun, is that everyone changes partners for each dance, and a community spirit is created each evening. It's easy to arrive alone and make new friends. And you may not even notice that you are getting a workout.
You can find contra dancing all over the country, in most cities, and some smaller communities. Here is one web page that describes it: http://bacds.org/camps/sprwkend2008/WhatIsContra/index.htm
If you search Google for "What is contra dancing", you will learn much more, and you may find a dance in your local community.