"Photoshop" is a pretty broad topic. The program was originally designed as a photo tool but now it's a very broad graphic arts program. Many books and online resources focus on teaching you how to use the entire program vs. just those features that apply to photography. Honestly, even though I sell images, I use a very small subset of the tools available in PS.
Lynda.com is a really good resource. For $25 per month (you can cancel anytime) you get all-you-can-eat access to a huge video library. That approach lets you target your learning to exactly what you're trying to learn. Scott Kelby's organization (NAPP) costs $99 per year. That membership gets you a monthly magazine devoted to teaching PS techniques as well as full access to the video library on their site.
lewiskemper.com is a good resource as well. Lewis is a local photographer (local to me) that has a series of training videos available on DVD if you'd like something more portable.
There are a ton of books available, and most of them are good, you just want to find something targeted at photographers vs. trying to learn the whole program.
Cheers