Computability Logic Homepage - Main online source on computability logic - a recently emerged formal theory of computational tasks and resources. Maintained by G.Japaridze. - http://www.cis.upenn.edu/~giorgi/cl.html
Introduction to Mathematical Logic - Hyper-textbook for students by V. Detlovs and K. Podnieks. - http://www.ltn.lv/~podnieks/mlog/ml.htm
Classical Logic - Introduction to classical logic, including completeness and Löwenheim-Skolem theorems; by Stewart Shapiro. - http://plato.stanford.edu/entries/logic-classical/
Mind Versus Goedel by Damjan Bojadziev - Compares the mind to advanced computers and artificial intelligence, as Goedel would possibly view them. - http://nl.ijs.si/~damjan/g-m-c.html
Mathematical Logic and Foundations - From The Mathematical Atlas, a resource of mathematics maintained by David Rusin. Extensive resources related to logic and set theory. - http://www.math.niu.edu/~rusin/known-math/index/03-XX.html