Complexity Theory

Probabilistically Checkable Proofs and Approximation - Pointers to some survey articles and their authors, by M. Bellare.
http://www-cse.ucsd.edu/users/mihir/pcp.html

Computational Complexity Theory - Definition of the subject, links.
http://www.cs.umass.edu/~immerman/complexity_theory.html

Theoretical Computer Science links - A collection of bookmarks to algorithms and complexity resources maintained by Heribert Vollmer at the Theoretical Computer Science Institute, University of Hannover.
http://www.thi.uni-hannover.de/en/research/links/

Complexity Zoo - Description of the 462 complexity classes and relations between them hosted at Caltech as a part of Qwiki project.
http://qwiki.stanford.edu/wiki/Complexity_Zoo

Automata, Computability, and Complexity, Spring 2005 - Course 6.045J / 18.400J at MIT OpenCourseWare with introduction to basic mathematical models of computation, Turing machines, Church's Thesis, time complexity and NP-completeness.
http://ocw.mit.edu/OcwWeb/Electrical-Engineering-and-Computer-Science/6-045JSpring-2005/CourseHome/index.htm

Complexity Theory - Two set of lecture notes by Prof. Oded Goldreich, Weizmann Institute.
http://www.wisdom.weizmann.ac.il/~oded/cc.html

Efficient algorithms and intractable problems - Course taught by Christos Papadimitriou and Umesh Vazirani at the University of California at Berkeley.
http://www-inst.eecs.berkeley.edu/~cs170/fa06/

Challenging Benchmarks for SAT and CSP - Includes related links, references and a summary of the results for the SAT benchmarks used in SAT Competition 2004.
http://www.nlsde.buaa.edu.cn/~kexu/benchmarks/benchmarks.htm

A Compendium of NP Optimization Problems - This is a preliminary version of the catalog of NP optimization problems.
http://www.nada.kth.se/~viggo/problemlist/compendium.html

Theory of Computation, Fall 2006 - Course 6.045J/18.400J at MIT OpenCourseWare, emphasizing computability and computational complexity theory.
http://ocw.mit.edu/OcwWeb/Mathematics/18-404JFall-2006/CourseHome/

Complexity of Algorithms - A list of topics from a Computer Science course involving complexity of algorithms. HTML and PS format.
http://artemis.cs.yale.edu/classes/cs460/Spring98/contents.html

ECCC - Electronic Colloquium on Computational Complexity - A forum for the rapid and widespread interchange of ideas, techniques, and research in computational complexity. Research reports, surveys and books; meetings, discussions and web resources.
http://eccc.hpi-web.de/

Computational Complexity and Programming Languages - Summaries of talks of the DIMACS workshop (July 1996), collected by James Royer.
http://www.cis.syr.edu/people/royer/talks.html

Computability and Complexity - An online course on complexity.
http://www.csc.liv.ac.uk/~ped/teachadmin/algor/comput_complete.html

Information-based Complexity - People, publications, prizes.
http://www.ibc-research.org/

Lecture notes on Complexity - Collection of lecture notes by Prof. Eric Allender, Rutgers University.
http://www.cs.rutgers.edu/~allender/lecture.notes/

Average-Case Complexity Forum - Introduction and survey papers.
http://www.uncg.edu/mat/avg/

Parameterized Complexity - Brief description, list of workers and problem compendium, compiled by Todd Wareham.
http://www.cs.mun.ca/~harold/W_hier/W_hier.html

IBM Research: Algorithms & Theory - An overview of computational models and methods and how they relate to complexity, with links to selected papers.
http://domino.research.ibm.com/comm/research.nsf/pages/r.algorithms.html

Computational Complexity Theory - Wikipedia article.
http://en.wikipedia.org/wiki/Computational_complexity_theory

Computational Complexity Theory - Course COMS 30126: Computational Complexity Theory, Department of Computer Science, University of Bristol
http://www.cs.bris.ac.uk/Teaching/Resources/COMS30126/

SATLIB - The Satisfiability Library - A collection of benchmark problems, solvers, and tools. Provides a uniform test-bed for SAT solvers as well as a site for collecting SAT problem instances, algorithms, and empirical characterisations of the algorithms' performance.
http://www.satlib.org/

Constraint Satisfaction Problems - Research group in the Computing Laboratory, Oxford University.
http://www.comlab.ox.ac.uk/activities/constraints/

$1 million for solving P vs NP - One of the Prize Problems named by the Clay Mathematics Institute of Cambridge, Massachusetts (CMI).
http://www.claymath.org/millennium/P_vs_NP/

SAT Live! - A collection of up-to-date links about the satisfiability problem (solvers, benchmarks, articles). A discussion forum is available as well.
http://www.satlive.org/