Sites

The Compleat Cladist: A Primer of Phylogenetic Procedures (Popularity: )
http://www.amnh.org/learn/pd/fish_2/pdf/compleat_cladist.pdf
A book about the basics of cladistics in PDF-format.

Understanding Cladistics (Popularity: )
http://www.amnh.org/exhibitions/Fossil_Halls/cladistics.html
Short introduction from the American Museum of Natural History.

What is Cladistics? (Popularity: )
http://www.fossilnews.com/1996/cladistics.html
The methods and terminology of phylogenetic systematics explained by the magazine Fossil News.

Introduction to Cladistics (Popularity: )
http://www.ucmp.berkeley.edu/clad/clad1.html
Cladistics is a particular method of hypothesizing relationships among organisms based on the idea that members of a group share a common evolutionary history.

Willi Hennig Society (Popularity: )
http://www.cladistics.org
Society of scientists studying cladistics.

Phylogenetics Methodology (Popularity: )
http://research.amnh.org/~siddall/methods/
Introduction to various phylogenetic statistical methodologies.