Below, I list 5 exercises that can be fun and present a bit of a challenge.

Tennis or Paddleball. Tennis and paddleball can be played all year round, and you can find courts that are open to the public for free. Check out courts located at public schools: some of them are open round the clock, and you can get in evening time when it's cooler. When looking for a racket, make sure to find one that has the proper balance and weight that you like. You can get them at any Kmart or Wal-Mart for a reasonable price.

Proform Ab Coremaster. This thing is a lot of fun, I'm surprised to say. There are all kinds of fitness products out there today that are designed to work your abdominal area. They don't all work. The Coremaster exercises are challenging, but you don't get the strain on your neck and back than you would with getting on the floor and doing situps and crunches (which I hate!)

Bike Riding. As a kid, I lived on my bike, and rode it everywhere I was allowed. I still like to bike ride, although I don't get to do it as much as I used to, I do the stationary bike thing more. Bike riding will give you a good cardio workout, and depending on how rough the terrain in your area, will help shape your legs.

Tae Bo. Billy Blanks Tae Bo combines martial arts and boxing techniques in an intense fat burning workout. And I do mean intense. Billy Blanks developed this program to lose weight and build muscle. I suggest starting with the kid's workout, especially if you're not in shape. You'll stay motivated all through the videos, and you'll evolve as the routines become more innovative - you'll challenge your body and your mind. Great for women, men and even kids.

Dancing. Consider taking some dance lessons. It's never too late to start dancing, even if you were never a dancer as a young put. Dance classes can be fun, they can help you to lose weight and change your shape. Consider Latin dance lessons. Latin dancing is fast paced: you'll work up a sweat, increase your endorphins, which will create a feeling of euphoria. Try to convince a partner to go along with you - while you can take dancing lessons alone, it's more fun with someone else.

If you've never done any of the above exercises, you can be sure you'll be sore for a while until you get used to doing it on a regular basis. Consider trying them all to see what works for you. Once you've find an activity you love, you will find that it is easier to stick with it.