The most comprehensive site to learn the basics of digital darkroom (no Photoshop, though) is also the biggest source of links I’m aware of: www.normankoren.com

Camera reviews site and forums: www.dpreview.com

Two extremely interesting and instructive photography and digital darkroom (Photoshop) web sites:  www.luminous-landscape.com; www.outbackphoto.com

Landscape & nature photography sites: www.topphotos.net