Cookbooks:

Photgraphy:
Canon: Enjoy! Digital SLR camera
Pentax: Technical pointers for those who plan to buy a digital SLR camera

Sensor cleaning:
Introduction - Please Read photo - Nicholas R. photos at pbase.com

For RAW processing:
Expose (to the) Right - Maximizing S/N Ratio in Digital Photography
The Art of Raw Conversion #011 - by Uwe Steinmueller
A very sharp image from a 24-70 F2.8 L...

For Sharpening:
Sharpening

For Black&White:
Better B&W - The Luminous Landscape Video Journal
Color to Black and White in PhotoShop - by Justin Winokur
Colour and Monochrome - Making a monochrome image
Converting colour images to black and white
Digital Black and White
Great Black and White conversions: Lab Color or Channel Mixer?
Lori's Web Graphics Ansel Adams-like Photos
Monochrome from Colour - by Ian Lyons
Pure B&W workflow with Capture One DSLR (C1) - by Uwe Steinmueller

For Duotones:
Bronze Quadtones for Photoshop
Duotones in Photoshop - luminous-landscape.com
Duotones - Jay Arraich’s Photoshop Tips

For effects:
Mishal's sketch technique

For general post processing:
DigitalRebel Photo Retouching
Photoshop for Photographers
Russell Brown Tips and Techniques
Stitching seqences - by "HockeyDave"
What is your favourite trick to enhance pics in one or two (max 3steps) in PS?

For Levels & Histograms:
What is a levels histogram?

For Printing:
B&W Printing With The Epson 2200 / 2100
Information On Black And White Digital Printing
Making fine prints in your digital darkroom Black & white
Monitor Profiling Kit Comparison and Ratings
Color management: Obtaining ICC profiles and building them with MonacoEZcolor
Paul Roark's Carbon Pigment & Variable-Tone B&W Printing
Paul Roark's Digital Printing Information Index

Learning:
Introduction to Color Spaces