That really depends on what you want to do with photoshop. Do you want to do basic photo processing or graphics manipulation? Make a collage or triptych? Create an advertising brochure for your business? Something else?
I like Russell Brown's tutorials although he's a goof. Much of what I learned I got off the retouching forum at
Digital Camera Reviews and News: Digital Photography Review: Forums, Glossary, FAQ. For basic tutorials, just use google. Photoshop is so popular that a ton of stuff is available on the web.
If you are just starting out, be warned, you will spend an ungodly amount of time learning image/graphics processing and printing/publication since they are incredibly complex topics. Photoshop is a great piece of software and has a ton of features giving you even more to learn. Two things I don't like about Photoshop - the price and lack of good noise reduction. Other than that it is top notch. OTOH, Picasa for free may provide everything you need. It all depends on what you're trying to do.
RG
Linear Mode
