Logic and proof: online resources
Introduction to Logic
A set of online tutorials for the study of elementary logic covering propositional and predicate calculus. Also an interactive Java applet with exercises.
An Elementary Introduction to Logic and Set Theory
An online tutorial including sentential logic, predicate logic and quantifiers, methods of proof, and naive set theory.
Logic for Mathematics by IMACS (Institute for Mathematics & Computer Science)
Choose "parents" or "students", then Mathematics & Logic from the submenu. This is an online course meant for mathematically precocious middle and high school students. This propositional calculus course introduces students to the propositional logic, a branch of modern mathematics which provides a rigorous mathematical analysis of the process of rational argument.
Logic & Proofs course from Open Learning Initiative (OLI)
Part of a full course that includes predicate logic and has been taught at Carnegie Mellon University. Click on the link "LOOK inside the free and open OLI Logic & Proofs Course" to see the course material.
How to Write Proofs
A 12-part tutorial on proof writing. Includes direct proof, proof by contradiction, proof by contrapositive, mathematical induction, if and only if, and proof strategies.
Cut The Knot
A site full of games, puzzles, illustrations, charts, paradoxes, illusions, mathematical droodles - often illustrated with interactive Java applets. You can learn a lot!