Other
Perpetual Motion Page: Machines
This personal site provides a good selection of proposed perpetual motion machines complete with drawings and detailed explanations of the machines.
Virginia Commonwealth University
Virginia Commonwealth Univ.: Work Definitions
This site from the Virginia Commonwealth University gives good information on the definition of work using nice graphics and interactive questions. Immediate feedback on student answers is provided.
Other
Tal Cohen's Bookshelf: The Emperor's New Mind
This site from the Tal Cohen's Bookshelf provides a detailed review of the book, The Emperor's New Mind. An interesting look at the machines of our world and how they may take on more human tasks.