I think the best way to learn CS4 is a task-oriented one. Pick something you want to be able to do. Go look at photos until you see a cool technique. Like the Cross-processed look, say. When google good ways to mimic that look in photoshop.





Then master it.





Then do it again with something else. Before you know it you'll have enough tools under your command to recombine and create in new and neat ways.