Yahoo answers is a place where you ask questions to get answers from common people. There are several how to jump higher questions available. You can find some valuable information from here. Do check it out and find what you are looking for. You can also post some questions and they'll be answered. It is an active community of people trying to help each other.
Here are some interesting questions I found while searching.
http://answers.yahoo.com/question/index;_ylt=AoNNx6ZnDc1OCosQFOBwOzYjzKIX;_ylv=3?qid=20061216172121AAjleAY
The person asking question says that he jumps rope 2000 times a day ( now that is one thing which you can use.)
http://answers.yahoo.com/question/index;_ylt=AhxvKDHIYU_jkUPUvSkc0cYjzKIX;_ylv=3?qid=20070907193712AAptQRi
This guy has some extra fat and is asking related to it.
http://answers.yahoo.com/question/index;_ylt=Atgy7KoW_8QNXEctuh7DdKMjzKIX;_ylv=3?qid=20061126055129AAGwXGm
Question on jump shoes
http://answers.yahoo.com/question/index;_ylt=AsuTfiMhRsOvCTEUuUy4n_QjzKIX;_ylv=3?qid=20071005235510AAbfm9x
About exercises for jumping higher
http://answers.yahoo.com/question/index;_ylt=AmLe2Fvbyg4MzLt0vDxjZesjzKIX;_ylv=3?qid=20070818135651AAkQ8hn
Whether jumping rope will add 5 inches
http://answers.yahoo.com/question/index;_ylt=AniaJSDNcXvUBYke.jioJQ8jzKIX;_ylv=3?qid=20070628025837AAxwMLz
A 14 year old asking about some exercises for jumping higher
http://answers.yahoo.com/question/index;_ylt=Al1SinLbWJxsK7KDksXzuc4jzKIX;_ylv=3?qid=20070717122521AAFGWyK
Asking the best technique ie. how much the knees should be bent
There are lots more on Yahoo answers. Just go to the site and search for how to jump higher or vertical leap or jump higher. If you cannot find what you are looking for, just ask about it. Who knows, you may find an answer that best suits you.