I am using CS 2.0. Most of the photoshop versions should have the features I use though (I think). I actually keep PS elements 3 (yes, the crappy freebie one) around because it's so much better for simple edits and photo organization.
As for how I picked up some new skills, I read about layer masks in a tutorial at Deviantart for anime art . . . lol
I also read a nice article on sharpening in a recent issue of PC Photo, and there was also an article elaborating on layer and mask use.
I started with anime art years ago though, and a lot of us use layers religiously so figuring out how to (ab)use layers with photo editing was pretty easy to learn. I'll try to make a tutorial myself so you guys can see what I do.