There's a few angles from using photoshop so I'll assume that you're coming at it from a photographers point of view. A nice place to start are the Digital Photography magazines.
The there's Photoshop Top Secret DVDs that I like but they're more arty, some examples are creating movie posters etc.
Also, if you have a video IPOD there are 100's of free subscription podcasts on PS tutorials everyday. You can also find photography videos here. My favorites are by Woven Shadows.
Amazing what you can find for free if you just search for it.