Sites

Mathematical Logic around the World (Popularity: )
http://www.uni-bonn.de/logic/world.html
A rich collection of links to logic-related websites.

Introduction to Mathematical Logic (Popularity: )
http://www.ltn.lv/~podnieks/mlog/ml.htm
Hyper-textbook for students by V. Detlovs and K. Podnieks.

Logic (Popularity: )
http://en.wikipedia.org/wiki/Logic
Wikipedia article.

Classical Logic (Popularity: )
http://plato.stanford.edu/entries/logic-classical/
Introduction to classical logic, including completeness and Löwenheim-Skolem theorems; by Stewart Shapiro.

Computability Logic Homepage (Popularity: )
http://www.cis.upenn.edu/~giorgi/cl.html
Main online source on computability logic, - a recently emerged formal theory of computational tasks and resources. Maintained by G.Japaridze.

Math Front: LO Logic (Popularity: )
http://front.math.ucdavis.edu/math.LO
Front end for the logic section of the mathematics e-print arXiv.

Mathematical Logic and Foundations (Popularity: )
http://www.math.niu.edu/~rusin/known-math/index/03-XX.html
From The Mathematical Atlas, a resource of mathematics maintained by David Rusin. Extensive resources related to logic and set theory.

Logic (Popularity: )
http://open-site.org/Science/Mathematics/Logic/
Open Encyclopedia entry. Hierarchically organized by subareas.

Mind Versus Goedel by Damjan Bojadziev (Popularity: )
http://nl.ijs.si/~damjan/g-m-c.html
Compares the mind to advanced computers and artificial intelligence, as Goedel would possibly view them.