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

QED Project - Build a single, distributed, computerized repository that rigorously represents all important, established mathematical knowledge

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.

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.