inkriminator

I'm sure this thread has been made before but I couldn't find it. I'm looking to be able to dunk, I'm 5'11" right now and can either touch rim or grab depending on how good I'm feeling that day. I'm hoping someone can suggest some exercises to increase jumping ability. I'm looking for primarily non-weight exercises, but if hitting the gym is necessary that's fine too. As for the intensity, I'd be willing to go as hard as possible. If anyone had a time-estimate as well that'd be great, thanks for the help