University of California
Ucmp: Introduction to the Archaea
Berkley offers an introduction to archaebacteria--ancient bacteria--including the history of the topic, scientific findings, and where to find archaeans. Includes images and links.
CK-12 Foundation
Ck 12: Biology: Prokaryote Classification
[Free Registration/Login may be required to access all resource tools.] Overview of classifying prokaryotes and prokaryotic domains.
CK-12 Foundation
Ck 12: Biology: Prokaryote Evolution
[Free Registration/Login may be required to access all resource tools.] An overview of the evolution of prokaryotes.