You may be interested in the "Double Your Vertical Leap" training course by The Vertical Project, but not sure whether it is really legit or not. I can tell you that this step-by-step program has worked for me, and my vertical jump has really doubled with it!
Having tried many other inferior vertical leap programs in the past, I have not only failed with them, but I felt that they have even taken away some of my leap inches! If you are looking to increase your vertical jump, I would advise you against trying other programs. Double Your Vertical Leap is the only proven vertical leap program you will need that works. See it for yourself below.