Hi V.,
I've no idea if anything out there is "free" but a few years ago, my husband (at my suggestion) bought me an elliptical machine for my birthday (Christmas is coming) and I love it. It's highly aerobic and low-impact. I also joined a local Curves. Definitely not free, but well worth it. They measure your progress monthly which for me was a huge motivator. What I liked most about it was the combination of strength training with aerobics that really helped the pounds drop off (I lost 60 pounds in about 6 months). The catch with Curves - aside from the cost - is that you get out what you put in. A lot of the ladies there seem to just go through the motions and don't get the results; socializing more than anything. But if you push it, you can get a really good workout in a little amount of time. If you find something free, I'd love to hear about it. I ended up dropping Curves because times are tight, but I still have my elliptical machine bought and paid for :-)