University of St. Andrews (UK)
University of St. Andrews: Search for Physics Beyond the Standard Model
This webpage is a picture site showing how different leptons interact.
Lawrence Berkeley National Laboratory
Berkeley Lab: The Particle Adventure
Visit this site for an interactive tour of the atom and all aspects of particle physics. View the animations available with almost every description on this site. A great place for the fundamentals of particles and forces including a...
Other
National Research Council: Elementary Particle Physics
The Committee on Elementary-Particle Physics, part of the U.S. National Research Council, presents this massive report on particle physics. It's a definitive document. Surprisingly readable, totally detailed. Start with the Table of...
Wikimedia
Wikipedia: Quark
This site from the encyclopedia Wikipedia provides an in-depth description of quarks describes different characteristics about them. Mentions how they are different from leptons, the theory of quantum chromodynamics, and the process of...
Other
Fermilab: Worldwide Discoveries That Led to the Standard Model
A thorough review of subatomic particles and the people that discovered them. Each particle has its own link for additional information.