The Tree of Life Web project
http://tolweb.org/tree/
Information about the characteristics of different groups of organisms and their evolutionary history.

The International Code of Zoological Nomenclature
http://iczn.org/iczn/index.jsp
This is the system of rules and recommendations that promotes stability and universality in the scientific names of animals and ensures that the name of each taxon is unique and distinct.

Palaeos
http://palaeos.com/vertebrates/index.html
This site provides information about extinct taxa of vertebrates.