These are links to general, broad resources on critical thinking.
Less Wrong Sequences – an organized series of posts on rationality topics, on the Less Wrong Wiki.
A Field Guide to Critical Thinking – a critical thinking primer published in 1990 in the Skeptical Inquirer.
Psychology of Intelligence Analysis – an online book on critical thinking, written by Richards J. Heuer of the CIA. It is written in the context of intelligence analysis but is widely applicable to all critical thinking.
A Tradecraft Primer: Structured Analysis Techniques for Improving Intelligence Analysis – a primer on intelligence analysis techniques based on critical thinking.
Critical Thinking and Intelligence Analysis – a paper by the National Defense Intelligence College.
Responsible Thinking – an online book on critical thinking, the scientific method, and the problems with false beliefs.
The Skeptic’s Dictionary – Critical Thinking Topical Index – an index to dozens of Skeptic’s Dictionary pages on a wide range of critical thinking topics.
Chapter 1 of “Becoming a Critical Thinker” by Robert Todd Carroll – additional chapters are available via the Critical Thinking Topical Index.
RationalWiki – a wiki of information on a wide range of topics, grounded on science, skepticism, and critical thinking.
Critical Reasoning for Beginners – videos, audios, and slides from a six-week course by the University of Oxford, Faculty of Philosophy.
Skepticism 101 – a large collection of educational resources on numerous topics in skepticism and critical thinking, from The Skeptics Society.
Harry Potter and the Methods of Rationality (HPMOR) – a fan-fic/parody (albeit a serious one) of the Harry Potter books, which posits how the story would happen if Harry Potter was a rationalist. Highly recommended.
ChangeMinds.org – a huge site on “all aspects of how we change what others think, believe, feel, and do.” This site is intended for sales and marketing people and others who need to learn the powers of persuasion. But is also an excellent resource for the would-be victims and targets of such persuasion.
Cognitive Biases and Logical Fallacies
These are links to resources that focus predominantly on cognitive biases, logical fallacies, and other human shortcomings of thinking.
Taxonomy of Logical Fallacies – a great resource on logical fallacies, from The Fallacy Files.
Learning and Teaching Resources
These are links to tutorials, curricula, and other resources for learning and teaching critical thinking.
Open Courseware on Critical Thinking – over 100 short tutorials on critical thinking, scientific reasoning, and related topics.
The National Center for Teaching Thinking (NCTT) – home page of the NCTT, which provides workshops and resources to help incorporate critical thinking into curriculum.
NSA’s Critical Thinking and Structured Analysis Class Syllabus – a detailed syllabus for a critical thinking course taught at NSA’s National Cryptologic School.
Informal Logic for College – syllabus, handouts, and related information for a “two-week intensive course” for High School juniors and seniors.
Reasoning Across the Curriculum Program – documents related to teaching critical thinking in all disciplines, from Prince George’s Community College.
Think Again: How to Reason and Argue – a free online course offered by Duke University, via Coursera. Part of a Duke University specialization certificate in Reasoning, Data Analysis, and Writing.
Critical Thinking in Global Challenges – a free online course offered by the University of Edinburgh, via Coursera.
Game Theory – a free online course offered by Stanford, via Coursera.
These are other sites that provide links to critical thinking resources.
Air War College critical thinking links – a large set of links to critical thinking resources, maintained by the Air Force’s Air War College.
Critical Thinking on the Web – extensive set of links to online resources on numerous critical thinking topics, maintained by Tim van Gelder.