Theory of Computation Lecture notes for an undergraduate class taught by Leonid Levin at UC Berkeley. http://www.cs.bu.edu/fac/lnd/toc/

An Introduction to the Theory of Computation An online text aimed at advanced undergraduate and graduate students. http://www.cis.ohio-state.edu/~gurari/theory-bk/theory-bk.html

Theoretical Computer Science on the Web A directory of resources related to theoretical computer science from Stanford University. http://robotics.stanford.edu/~suresh/theory/theory-home.html

Church-Turing Thesis Wikipedia article. http://en.wikipedia.org/wiki/Church-Turing_thesis

Computability Theory Wikipedia article. http://en.wikipedia.org/wiki/Computability_theory

Interactive Computation Wikipedia article. http://en.wikipedia.org/wiki/Interactive_computation

Computability Logic Main web source on the subject: overview, downloadable articles, links. http://www.cis.upenn.edu/~giorgi/cl.html

Inspec English-language bibliographic information service providing access to scientific and technical literature in physics, electrical engineering, electronics, communications, control engineering, computers, computing, information technology, manufacturing and production engineering. http://www.iee.org/publish/inspec/