A Century of Controversy over the Foundations of Mathematics: Edited transcript of a lecture by Gregory Chaitin, author of `The Unknowable'.
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.
FOM: A closed, moderated, e-mail list for discussing Foundations of Mathematics moderated by Martin Davis. Archive available.
Foundations of Mathematics: This is a site for studying foundations of mathematics, or it can be used as a reference material. The site is structured as contents pages of a book on the subject of mathematics foundations. It comprises links to expository materials.
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.
Mizar Project: An attempt to reconstruct mathematical vernacular into a formal language which can be read by humans and also verified by software.
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.
QED Project: Build a single, distributed, computerized repository that rigorously represents all important, established mathematical knowledge