We have a gender-free Contra Dance in JP at First Church of Jamaica Plain once or twice a month - usually on the 2nd or 4th Saturday, but not always.
The next one is Saturday, April 14 at 7:30-11PM. I created an event for it (I'd invite people from the JP Dance group but I don't know how to do that).
Come try it out. It's lots of fun - beginners are welcome; you'll learn what you need to know to participate. See the event or http://www.lcfd.org/jp for more info.