Start with a PS book that focus' on what you will do most. Whether that is photo processing, creating banners, whatever.
Then, there are hundreds of tutorials on the web.
Here is a site to get you started:
http://www.good-tutorials.com/
See if you can learn from them. If so, forget the courses and training CDs.
And when you use a tool for the first time in a tutorial, spend a few minutes to understand the various ways it can be used.
In two years, you will be a master at PS!
