Dead Logicians Society - http://www.freewebs.com/deadlogicianssociety/ Warwick university's very own logic society aiming to increase and stimulate interest in logic and philosophy of logic at the university. Offers news and events.
Frege's Theorem - http://plato.stanford.edu/entries/frege-logic/index.html Article in the Stanford Encylcopaedia of Philosophy, entitled `Frege's Logic, Theorem, and Foundations for Arithmetic'. Discusses the 1980 discovery of Crispin Wright that Frege's work of the Grundgesetze can be carried out in second-order logic with Hume's principle.
Peirce's Logic - http://plato.stanford.edu/entries/peirce-logic/ Article in the Stanford Encyclopaedia of Philosophy, by Eric Hammer.
Logic - http://www.philosophypages.com/lg/ An online textbook by Garth Kemerling, explaining the basic elements of elementary logic at an undergraduate level.
Why Aristotelian Logic does not Work - http://www.abelard.org/category/category.htm An essay at Abelard.org outlining an argument against Aristotelian syllogistic.
The Logic Course - http://www.thelogiccourse.com/ An interactive course in formal logic, with tutorials and quizzes on critical thinking, truth-tables, and sentential.
PHILOG - http://www.philog.ruc.dk/ The Danish Network for Philosophical Logic and its Applications.
Nordic Journal of Philosophical Logic (NJPL) - http://www.hf.uio.no/filosofi/njpl/ Edited at Dep. of Philosophy, Univ. of Oslo, published by Scandinavian U.P. in hard copy and on WWW. Full-text Web edition free for personal use.
Symbolic Logic - http://www.earlham.edu/~peters/courses/log/loghome.htm Online resources provided to supplement undergraduate course taught by Peter Suber. Good collection of handouts.