Lessons and Tutorials from an Adobe Photoshop CC Certified Expert

Beginner level: 

Luminance and color corrections, working with levels and curves inside photoshop, true black and white conversion, shadows and highlights adjustments, cropping, resizing and saving images especially optimized for the web and high quality printing.

Intermediate Level: 

Cleaning skins with spot healing adjustment brushes, making tonal corrections on the skin, color correcting eyes, teeth, lips, hairs,
adding and removing color tones, introduction with Photoshop Layers, creating vintage style photos, changing the shape of the objects and portrait retouch basics. Introduction to basic selection techniques. 

Advanced Level: 

High end portrait retouch, tools and techniques creating that perfect skin, adjusting eye highlights and changing the overall light balance, dodging and
burning technique for creating that glamour look found in todays magazines, working with Camera Raw for restoring correct white balance and exposure
(camera raw is the software that comes with photoshop for processing digital negatives before opening the image with photoshop), frequency split technique for high end skin retouch, compositing different images into one scene with the correct color matching, advanced selection techniques. 
HDR (High Dynamic Range) photography techniques with photoshop and your camera. Plus any other technique you would like to know.