Here are some of my favourite websites:

 

Luminous Landscapes

Great for how-to's, reviews and essays.

Scott Kelby's Blog

Good tips, ideas and guest photographer bloggers.

Lightroom Killer Tips

Self-evident. I consider Adobe Lightroom an essential tool.

Thom Hogan

Nikon-centric product reviews and market analysis.

Digital Photography Review

New product reviews.

DCViews

New product reviews.

PhotoMatters

This is a great site for beginners and intermediates. It illustrates and explains numerous photo settings and techniques. It "explores the creative variables of photography, one at a time, to see how each works".