As someone who taught Photoshop professionally for a year (aka, made the majority of my living teaching the program in cities across the US in one day intensive courses) I came to a few realizations not only about Photoshop, but about computer programs in general. The largest lesson I learned is there's always more to learn, so realize great art can be created with the simplest of techniques. Learn the simplest possible techniques, and then push those to make things work knowing only those few basic tricks. There's probably a quicker way, but until you learn the dumb way, don't expect to move on. Only learn new skills when you hit a wall with the old ones. Art works best with limitations.
There's a base level in any program that needs to be know before you can use it. In Word, it's the ability to open it up, type, and save. In Photoshop the base requirement is a bit more. In 3d programs like Maya it's larger still. Mastering all the shortcuts and caveats is not the major hurdle. In fact, trying to learn all those stupid little tricks is a waste of time. Again, do everything in the simplest way possible, and plan to learn better methods eventually. All programs share a common trait. The major hurdle is one of deeper skill.
To be good at Photoshop takes about a day's worth of technical training (obviously only if done right). After that it's a matter of having a cheat sheet by your side with the shortcuts, and knowledge of what website or book you can quickly learn about how to do X. Usually google is the second best resource, with the right book being a far better help. Too many people use google as the only resource, and end up spending an hour searching how to do every little thing.
The far greater hurdle (after the technical one is learned in a day. Maybe two) is the artistic side of things. Becoming a good photographer takes skill. As does thinking of creative ways to combine images, as well as ways to experiment with the art of photography. Learning how to paint takes a long time, as does learning how to design. Combining all these disparate skills in a way that only Photoshop can is very much the last step in a long learning process, and too many people think it's the first. They think the simple act of opening up Photoshop will turn a person into a great artist.
While it's true that some out there are looking for nothing more then the ability to crop images and take out red eyes, there are that many others looking to expand the bounds of their artistic abilities.
It frustrates me that people think learning the technical side of anything will make them a good artist.
So with that in mind, I won't bother pimping out the classes I used to teach through Skillpath or the class I one day plan to start through Exus Training, if I ever get my act together to market it. Honestly, until I have a very large group of online followers or team up with a good marketer, I really don't see it happening. I had no idea how crucial and how difficult spreading the word, even about excellent products, is.
For those interested, here' s the best books out there, that I tell people are good to buy for Photoshop. Honestly, if you want to learn the program-stop wasting your time on 'excellent' sites. Break down and spend the money for a book. It will save hours, if not weeks or even years. This is because it sits right by your side to be referenced instantly without the distraction and disinformation and misinformation of the internet. I learned Photoshop the stupid way. Hopefully you won't have to.
Adobe Photoshop CS3 One-On-One by Deke McClelland is hands down the best starter book. It's a good resource, and also works as a good read. He's funny. The examples are engaging, and more importantly, relevant. On a personal level, this book worked as a great guide for how to structure teaching my own classes. I'd suggest the CS4 One-on-One book, but I figure you'd prefer saving the $15. If you only get one book, this is the one.
As far as starter books go, I'd avoid Photoshop CS4 Classroom in a Book and Photoshop CS4: Visual Quickstart Guide. They're good, but not as good. Also avoid Photoshop CS4: The Missing Manual. From what I've heard, at 800 pages, it's way too much needless information pretending to be relevant. Looking at the amazon reviews, that might be true of old versions of the missing manual, but not this one.
The next book I'd suggest, which basically goes into a methodical process for approaching any image is Scott Kelby's 7-Point System. It takes you through how to get a fantastic image, starting with the normal half way decent dreck coming out of the camera. He hammers in his points of these are the 7 steps needed for absolutely every photo, and in that way, gets people thinking in a Photoshop mindset. It's all about case study after case study after case study.
Once you consider yourself an expert, check out Professional Photoshop: The Classic Guide to Color Correction (5th Edition) by Dan Margulis. It's needlessly verbose, and very tough to get through, but absolutely fantastic. It doesn't get into the technicals of Photoshop. It assumes you know those. What it does is make you perfect at color correction, and gives an understanding of how digital images work and how to get them to do whatever you want at a much deeper level then you thought possible. I thought I knew just about everything about the program when I picked up this book. Turns out I knew nothing. He has another book dealing just with LAB color mode, but I'd get them one at a time.
So those are my book recomendations. Past that it's a matter of working on the core skills - painting, photography, and design. A life time pursuit that's no small order.
If you insist on looking at websites, check out the tutorial list compiled at Elite by Design.
Once you get a fundamental understanding of the program (let's put that at knowing 3 dozen shortcut keys by heart, and not needing to look up a tutorial if you want to do something like metallic text. Better yet, you know better then to do metallic text in the first place.) then you should start using the internet.
Smashing Magazine is always a great resource, as is PSD Tuts. Hunt around as needed, as there's so many great resources out there once you know what you're doing. For the latest in CS4 and a collection of cheat sheets check out 64 essential guides, tips and tutorials to definitely master Photoshop like a pro.The web alone is a horrible and slow way to start learning any program, but it certainly has its place.