What are some of the best ways to improve Flexibility?

Yesterday, my son told me that the varsity catcher is taking yoga classes for that very purpose.

Yoga classes are excellent. I've got an MLB club's off-season training manual for their minor leaguers and it specifically states to enroll in a Bikram Yoga class, not just for catchers, but for all players.

Another excellent activity that will help your flexibility and balance, focus, etc. is to take a martial arts class. A year of that will give many benefits that will help you on the diamond, as well as off. Finally, focus on stretching AFTER you've worked out. Warm muscles stretch better than cold ones. Don't overdo it or rush it, gaining significant flexibility takes time.

Catchers should take more time stretching then just the amount your time may stretch for. Taking the time to stretch your groin, quads, hamstrings, glutes, and calves can reduce injury and keep you fresh throughout the season. There is a catching specific video you can watch for free if you would like. Let me know.
Brian