Hilbert II - Mathematical Foundation Project
- The Goal of Hilbert II, which is in the tradition of Hilbert's program, is the creation of a system that enables a working mathematician to put theorems and proofs (in the formal language of predicate calculus) into it.
- http://www.qedeq.org/

Foundations of Mathematics
- Reviews the foundations of mathematics with reference materials structured as content pages of a book. Includes links to expository materials.
- http://sakharov.net/foundation.html

FOM
- A closed, moderated, e-mail list for discussing Foundations of Mathematics moderated by Martin Davis. Archive available.
- http://www.cs.nyu.edu/mailman/listinfo/fom/

Arché
- The Arche project looks at the foundations of mathematics, especially at Frege's Theorem and its ramifications. Based at the University of St Andrews.
- http://www.st-and.ac.uk/academic/philosophy/arche/

A Century of Controversy over the Foundations of Mathematics
- Edited transcript of a lecture by Gregory Chaitin, author of `The Unknowable'.
- http://www.umcs.maine.edu/~chaitin/lowell.html

Practical Foundations of Mathematics
- Online text of the book by Paul Taylor, together with supporting materials. The text aims to provide a conceptual and formal foundation for mathematics and computer science.
- http://www.dcs.qmw.ac.uk/~pt/Practical_Foundations/

QED Project
- Build a single, distributed, computerized repository that rigorously represents all important, established mathematical knowledge
- http://www-unix.mcs.anl.gov/qed/

Mizar Project
- An attempt to reconstruct mathematical vernacular into a formal language which can be read by humans and also verified by software.
- http://www.mizar.org/