There are a really cool set of books by a guy named Scott Kelby, including photoshop down and dirty tricks, killer tips, classic effects etc.
he takes you from the basics right up to collages, pro advertising techniques and all but does it in a way that is quick and very easy to follow with lots of tips, tells you what the short cut is, illustrates and directs so well that I have a number of his books and regard them as a reference
I HIGHLY, HIGHLY recommend you check them out
http://www.scottkelby.com/books.html
http://shop.scottkelbybooks.com/index.php
Cheers
John