Cloud computing is a new and emerging area, so new that each person can have his own definition of what "cloud computing" is.
In their paper Above the Clouds: A Berkeley View of Cloud Computing a group from Berkeley explains their definition, and discusses the benefits as well as the challenges that cloud computing brings.
You can find my slide set for this topic here: Cloud Computing Infrastructure - ppt, pptx
Beside discussing the mentioned above paper, I also include a brief description of Amazon EC2 and Google AppEngine, two of the biggest cloud providers currently in the market.
