From suite101.com:
Introduction to Plyometrics (http://www.suite101.com/content/an-introduction-to-plyometrics-a237186)
Plyometric Training (http://www.suite101.com/content/plyometric-training-a135203)
Improve Your Vertical Leap (http://www.suite101.com/content/exercises-to-improve-vertical-leap-a134526)
Improve Your Jump (http://www.suite101.com/content/improve-your-jump-using-plyometrics-a215419)
Good stuff!!!
Remember to always be instructed in plyometrics by an individual with a background in a health science related field. If done improperly, with incorrect technique or too many, a skater can get injured. There is also a progression in plyometrics that must be followed, progressing from a basic to advanced level.
For those people who can't afford a personal trainer, need a refresher course, or just some inspiration, this is a great free resource. Plus, it's not as complicated as many plyometric sources - these are just simple exercises explained well and in a building-block order. I liked it a lot.
I once worked with an eastern-european coach who required simple daily plyometrics for all his students. He did a weekly off-ice class with them, but then expected them to do off-ice by themselves (or with a buddy) every day. I think it helps to get started and check in with a trainer regularly, but if you're a self-starter or can keep a routine, DIY works.