Website about mathematics
- the nLab: a researh level wiki about (fundamental) mathematics with the point of view of (higher) category theory.
- the n-Category café: the community blog that has given birth to the nLab.
- MathOverflow: a research level forum about mathematics.
- MathStackExchange: an undergraduate level forum about mathematics.
Website of other people
- Clemens Berger
- Paul-André Melliès
- Joyal's CatLab: André Joyal's own category theory wiki.
- Pablo Rauzy on Open Access.