The Sisters of Fraternity Notre Dame set up a soup kitchen in New York in 1991. They also work with AIDS patients. They do not proselytize, just work to serve others. But they picked up a hobby!
Shortly after their arrival, they began to study the martial arts. The thought of using it on the streets to protect themselves was not the reason they began training. It was purely for exercise and recreation. One of the sister's, Mary Chantel, had earned a black belt in judo before entering the convent. She was eager to resume the sport and found a place for all of them to work out.
Witness Magazine has a photo essay on the sisters, including several karate pictures near the end. http://visionproject.org/mag/nuns/index.php -via Metafilter