Cloud Computing and Emerging IT Platforms: Vision, Hype, and Reality for Delivering Computing as the 5th Utility
http://www.gridbus.org/reports/CloudITPlatforms2008.pdf

This article particularly includes details (1) on Characteristics that differentiates Clouds from Grids (and Clusters) and (2) a case study on building 3rd party services using commercial Cloud infrastructures. This has been added to Grid Resources Subject Tracer™ Information Blog.