Want to raise money for your charity without spending a cent? These three programs will let you turn every drop of sweat from your next workout into cold hard cash for your favorite charity.

Charity Miles. Download this free iPhone/Android app to raise money for your favorite cause every time you walk, run or bike. Just choose a charity and press start. As you exercise, the app tracks your distance and you earn money for your charity. Bikers earn 10 cents per mile; walkers and runners earn 25 cents per mile — up to the app's $1,000,000 sponsorship pool.

Charity Bets. Choose an event. Set a goal. And let friends and family members "bet" on whether or not you will hit your mark. You'll train your heart out knowing that your favorite charity is counting on you. And you will both reap the rewards as a result.

Plus 3 Network. Log your exercise with this app and every mile on the treadmill or lap in the pool will be translated into points that are converted into dollars to be donated to your favorite charity by corporate sponsors. Use a GPS device to track your progress and you'll earn double points.

Related charity story on MNN: 8 well-rated charities to kickstart your holiday giving

Turn your next workout into a charity fundraiser
Three sites that let you use your next workout to raise thousands of dollars for charity.