Tennis Anyone?

I signed William and myself up for tennis lessons starting next month. Should be fun, I've always wanted to play. I have also starting some belly dancing. I am doing the videos right now and if I get better at it I will take some classes. Right now I am not very "sexy" at it though. I was invited to take some Krav Magao (or Maga depending on your source) classes, but that may have to wait until Tennis is done. I have always enjoyed Martial Arts and practiced different forms for about 10 years, but l realize that all of my "extracurricular" activities get expensive. I love learning different things and finding "fun" ways to exercise. I even took ballet with one of my roommates. So what's a fun way you keep in shape?