Gymnastic rings are a terrific tool for tons of exercises. Pull-ups, muscle-ups, dips, to name a few movements that can be taken to a whole new level with rings. I recommend using 1″ pvc, but I made mine out of 3/4″ and they have done fine. Click here for instructions on how to make your own rings. It is inexpensive and easier than you think
Perform dips, push-ups, L sits, V sits, hand stands, and other bodyweight gymnastic movements. Increase upper body strength, balance, and body control with inexpensive homemade parallettes (PDF.)
Parallette training will unleash the gymnast within and develop that super-human gorilla strength. Talk about throwing a monkey wrench into your workout and confusing the heck out of your muscles. A steady dose of this will give those stagnate muscles no other choice but to grow stronger.