I've recently been spending a lot of time trying to learn Photoshop CS4 whilst going through a number of training video's from http://www.kelbytraining.com/. I have to say the video's are first rate.
I also bought a good Photoshop CS4 book which is a loose step by step guide which is also very good, well it should be as I spent most of the afternoon in Waterstones Picadilly Circus branch whilst on a recent trip to London.
The Two books are as follows (Both highly recommended):
Photoshop CS4: Essential Skills (Photography Essential Skills) by Mark Galer
Photoshop CS4 Down and Dirty Tricks (Down & Dirty Tricks) by Scott Kelby
Also finally found a serious use for utube, it is full of example Photoshop training video's, some serious, some a little tongue in cheek.
In a few weeks I will put some of my 1st attempts up here for you to have a look at.
By for now.