If you just remember that your shoulders are the most versatile single joints in your whole damn body, you can get a real good pec workout just using push-ups. Think about it this way; stand up, arms length from and facing a wall. Now think about all the positions you could swing your arms to on that wall: the same applies to your push-ups. Arms close, wide, staggered, out of parallel, fingers pointing in any direction you can manage, up on your knuckles, or even fingertips. And don't just think about straight up and down; think about your head tracing patterns in the air and in more than one plane; circles, shapes, letters. And last but not least is tempo; slower reps will build tendon and ligament strength along with muscular development. Quicker reps improve speed and oxygen uptake function; if you're looking for hand speed and punching endurance, don't forget your shoulders, triceps etc. for this also. And last, but not least; slow-down, (4-6 seconds) and blast-up, (fast as you can, maybe even clap once or twice) builds explosive power. Vary the width of your feet, or just use one. Arch your back up, or even stick your butt up in the air (dive-bombers), to target the upper curve of your pecs. Get three chairs, one for the feet, and let your back droop to target the lower third of your pecs. Get creative, experiment and, most importantly; feel what works best for you, build up to one arm push-ups and build on success. Once you get REAL good think about doing push-ups/flys on the
hanging rings or in a crossover rig.
Good luck !