Georgia State University
Georgia State University: Hyper Physics: Leptons
This site has a definition and properties of Leptons, the "Basic building blocks of matter." There are links to table of properties and more information.
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: Leptons
This particle physics tutorial discusses the different types of leptons: the electron, tau lepton, muon lepton, and neutrinos.
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.