BJ Fogg of the Stanford Persuasive Technology Lab at Stanford University has created a learning module for evaluating the credibility of web sites:

Learning objectives

In this module students will:

• Learn the meaning of credibility and captology – and how they relate to each other.

• Understand why designing websites for credibility is important.

• Become familiar with guidelines for credible website design.

• Learn about research insights relating to Web credibility.

• Gain a theoretical understanding of how people evaluate credibility.

What I have linked to above is only part of the curriculum, which Fogg gave me permission to publish online. There is also a presentation associated with the learning module. Fogg says that he plans to "send a (free, of course) personalized version to each academic who wants to use the material. This way I get a sense of who is using the material, and I can start developing a collegial relationship." If you're interested in using the module, you can contact Fogg at bjfogg at stanford dot edu.