10 Tips for Teaching Critical Thinking — From Edutopia, based on a KIPP school, but still good :)
Brief Guide for Teaching and Assessing Critical Thinking in Psychology — article written for undergrad Psych professors, but very helpful to us as well; useful table on quality of evidence
The Critical Thinking Community — a site with great resources - collaboration of several organizations that promote the teaching of critical thinking in K-12 and college education