If you're a photographer and you regularly use Photoshop (who doesn't) and you don't know who Scott Kelby is... well, you should.
Scott Kelby is probably most well known as one of the "Photoshop Guys"(along with Dave Cross and Matt Kloskowski). However, he's also a talented photographer with an unfailing desire to teach anyone who will listen about anything related to photography and digital arts.
Close to everything I know about Photoshop and Lightroom has come from either one of Scott's videos/books or his blog www.scottkelby.com. In fact, the first Photoshop Elements book I bought was by Scott Kelby (I have to admit, at the time I really didn't know who he was... but I should have).
Scott has a simple way of teaching that cuts through all of the unnecessary verbiage (aka BS) that a lot of instruction books come with. He has also amassed a stable of amazing talent for Kelby Training. You can find everything from Photoshop, Lightroom, digital design to general photography and lighting techniques. It's well worth the investment so check it out at www.kelbytraining.com.
You can also find a lot of free tips at Photoshop User TV. If you're still looking for more then you should consider joining NAPP (National Association for Photoshop Professionals). At last check there were over 60 pages of tutorials.
By profession, I work in learning and performance so I really appreciate "just in time" learning (hey, we're all busy and sometimes we need to get in quickly, grab what we need and move on). Well, that's what you get with pretty much all of the resources mentioned above. You can spend hours going through as much content as you wish in one sitting or find exactly what you need quickly.
Tons of learning so I hope you check out some of these resources.