Wikimedia
Wikipedia: Punctuated Equilibrium
This brief explanation of punctuated equilibrium includes paragraphs on the history of the theory and the controversy surrounding it.
Other
Principia Cybernetica Web: Punctuated Equilibrium
Starts with a definition of Punctuated Equilibrium, followed by an explanation of this "Observation," and how it fits with other evolutionary theory.
Stanford University
Stanford Presidential Lectures: Stephen Jay Gould
Standford University provides interesting biographical and professional information on Stephen Jay Gould and his many contributions to scientific thought, including his efforts to help people see science "As something that is important...