Lighting in games.
Practical Light and Color ($) by Jeremy Vickery - video by a lighting artist at Pixar
Light for Visual Artists: Understanding & Using Light in Art & Design ($) by Richard Yot
Color and Light: A Guide for the Realist Painter ($) by James Gurney - lighting from a painter's perspective, lavishly illustrated.
Painting With Light ($) by John Alton - cinematographer's guide to lighting.
Digital Lighting and Rendering ($) by Jeremy Birn - digital artist's guide to lighting.
Lighting Basics and You... thread on the Polycount Forum.
PSG Art tutorial by Arne Niklas Jansson