Standard Model

Information on the Standard Model and a Possible Difficulty
Introduction to the Standard Model. The site also contains links to other topics such as neutrinos and electroweak-symmetry-breaking/mass-generation.
http://www.jupiterscientific.org/sciinfo/smtrouble.html

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).
http://particleadventure.org/particleadventure/frameless/standard_model.html

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.
http://blueflag.phys.yorku.ca/yhep/main.html

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.
http://arxiv.org/abs/hep-ph/9812242