ChromeSphere has a very nice overview of optics (the behavior of light), with a particular emphasis on how those concepts translate into the 3D world, working with materials (textures, shaders), and so on. Really good stuff.

Thanks, Renderosity.

Related reading:

• Lighting Techniques by Amaan Akram
• 3D in Depth: Lighting by Nathan Segal
• 3d Lighting Setups: 3 Point Lighting by Jenn Downs