-There is a bunch of QuickTime Video Tutorials in this link here.
-Scott Kelby is a prominent author. His latest title - [ame="http://www.amazon.com/gp/product/0321330625/qid=1146968457/sr=1-1/ref=sr_1_1/104-3681884-0060744?s=books&v=glance&n=283155"]Photoshop CS2 Book for Digital Photographers[/ame]
I use photoshop, because I was able to get it through work.
For some things, however, notably adjusting contrast (outdoor photos when the subject's face is in the shade) Picasa, available free from Google, works so well, it's almost spooky.
One big advantage of Photoshop, besides the fact that it will do, well, everything, is that there's a monthly column in Popular Photography that explains all kinds of nifty techniques.
for tonal changes, brightness, contrast, and all the 'normal' stuff, then there are ALOT of editing programs to use. For heavy-duty touch ups, layering, masking, etc., Photoshop is pretty much king. I've become quite used and really enjoy using it.