Here are a couple of cool websites that I've found that have to do with lighting.

Strobist: This website has a wealth on information on lighting, particularly hot shoe flashes used off camera. It goes in depth from the basics to more complicated lighting.

Guess the Lighting: Photographer Ted Sabarese analyzes popular ads and images and describes how he thinks they were lit and draws lighting diagrams.

Top 10 lighting facts: These are pretty obvious, but knowing/remembering them can really help with making changes in the studio.