You might also consider trying DDR if you like to dance. I don't know if you've heard of it, but I'll explain..
You'd need a playstation 2(~$150), a pad (~$40) and the game (~$50), so it IS a big investment if you don't already have a PS2. There might be a version for playstation 1, also, and you can probably find all of these things for much cheaper at ebay, etc.
You can also go to most arcades, and chances are they will have a DDR pad set up and you can test it for like $1 a song or something. That way you can see if you like it! It has a calorie counter, and you can change the songs, monitor your weight progress, and adjust the speed of the songs.
Basically, you dance on a pad and try to match the steps that the game shows you. There are a bunch of different moves, and it takes a lot of skill to keep up. It's very challenging, and if you like to dance, this might be something you could check out.