OP.....while not nearly the cardio exercise of roller blading, if you are looking for a fun and challenging new sport to pick up, why don't you try Disc Golf? It can give you a bit of a workout depending on the course and how rugged the terrain is, and is very inexpensive as most courses are free to play with an initial startup cost of about $20-$30 to buy a set of discs. If you like the outdoors you'll enjoy the varying courses, and if you are a stoner a lot of people like to toke in the middle of a round because oftentimes you are in the woods off the beaten path away from everyone else.
Its also a sport that isn't really gender dominant, meaning as a female as you work on your game you can be just as good as any guy once you get your technique, form and shot selection down. Its something you can play very casually or very competitively....its pretty much whatever you want to make it.
Here's a link to find the nearest disc golf course near you, just enter a zip code and they'll give you a good idea what is around your area...
http://www.dgcoursereview.com/I wouldn't exactly call it an "unpopular" sport as its been growing quite a bit in the last several years with courses popping up all over the place....but still not that many mainstream people are actively playing it or talking about it much.
