Programming

• Web design: A tutorial on how to control <DIV> layout using CSS.
• Why's (Poignant) Guide to Ruby - excessively silly, yet informative.

Photography

• Ken Rockwell's reviews of Nikon products, lenses especially. Particularly his page on the best and worst lenses Nikon makes.
• Strobist, the blog about how to light your shots with a cheap, light kit.