Frege's Theorem  
   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 Hum
   http://plato.stanford.edu/entries/frege-logic/index.html

Logic and Mathematics  
   Essay on the nature of logic and its relationship to the philosophy of mathematics, written by Stephen G. Simpson.
   http://www.math.psu.edu/simpson/papers/philmath/

Why Aristotelian Logic does not Work  
   An essay at Abelard.org outlining an argument against Aristotelian syllogistic. The argument focusses upon the relationship between Aristotle's categories and his conception of being, attacking them from an idealist position drawing upon Brouwerian intui
   http://www.abelard.org/category/category.htm

The Troublesome Paradox  
   Online version of book seeking publication by Per Lundgren. Author attempts to argue that a consequence of Goedel's incompleteness theorem is that we should overturn our current approach to scientific method.
   http://www.yesgoyes.com/

Logic  
   An online textbook by Garth Kemerling, explaining the basic elements of elementary logic at an undergraduate level.
   http://www.philosophypages.com/lg/

Peirce's Logic  
   Article in the Stanford Encyclopaedia of Philosophy, by Eric Hammer.
   http://plato.stanford.edu/entries/peirce-logic/

Philosophical Logic  
   Introductory article by E. J. Loewe.
   http://www.dur.ac.uk/~dfl0www/modules/logic/PHILLOG.HTM

Nordic Journal of Philosophical Logic (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.
   http://www.hf.uio.no/filosofi/njpl/

Symbolic Logic  
   Online resources provided to supplement undergraduate course taught by Peter Suber. Good collection of handouts.
   http://www.earlham.edu/~peters/courses/log/loghome.htm

PHILOG  
   The Danish Network for Philosophical Logic and its Applications.
   http://www.philog.ruc.dk/

Tips on Translating English into First-Order Logic  
   An introductory guide by Peter Suber.
   http://www.earlham.edu/~peters/courses/log/transtip.htm