Resources for Learning and Teaching Critical Thinking

Critical thinking is a 21st Century Literacy everyone should be familiar with, but how do you learn it? or teach it?

Howard Rheingold and a group of educators have created the Critical Thinking Compendium with resources such as tools which includes a great list of resources to help students (and anyone) evaluate resources they find online.  Definitions are offered on the vocabulary page and  there is even a Diigo Resources page