Creative Cow is the daddy!!
Getting a book from Amazon or E-Bay is probably your best bet but i find training videos are invaluable. They tell you what you want to know fast and at a step-by-step pace. Plus the best thing is if you like in the right places on the web you can find them for free!!!
So give the following places a try: -
Creative Cow is probably the best place to go as they have just countless videos. My advice to you would be to get a book to learn the basics and then once you feel more comfortable with what the program can do then start looking at Creative Cow.
Hope this helps.
All I want to do with the rest of my life is Edit.