I take tutorials from lynda.com on line. They have many photoshop courses including CS5. A one month membership will make you an expert. You can take as many courses as you like during the month.
CS5 is night and day over CS4, I also recommend Lynda.com and also check out Kelby Training and any of his books that go along with the various products Adobe makes
I ran a group years ago, and have to say that the information and materials supplied to the groups from Adobe (and Macromedia back in the day) are excellent.