After many years of playing around with 'junior' software such as PaintShop Pro (which is actually pretty good) I've broken down and bought Photoshop CS3 and am now faced with the daunting task of learning how to use it.

Can anyone suggest on-line resources and / or tutorials which would be good places to learn more? I've got many of the basics covered, but am interested in learning more about curves, tonal corrections, layers etc.