Run!
I love my weekly jogs! Yes, they're a great way to burn calories and tone your legs. I wear a HR monitor (great investment, especially for running) and although I'm fit, my HR gets really high, so I add little walks to lower my HR. So it's definately an intense workout- I don't know how it can't be.
Just go slow in the beginning- you WILL most likely be sore (I still get sore even if I miss just 2 runs). And don't do too much too soon since it is high impact. And stretch!
Good luck, and enjoy the nice fall weather- perfect for runs (depending where you live)!