Particle Adventure's Standard Model - A popularization of the physics of the standard model. (The website is somewhat slow unless one has a broadband connection).
Particle Physics - An introduction. For Standard Model information, click on the third item in the index. The site provides brief descriptions of a variety of particle physics topics.
The Standard Model - Lectures at the graduate and post-graduate level providing an introduction to the basic aspects of the Standard Model. Available in postscript and PDF formats only.