Here is list of some famous mathematics blog, magazine and websites
Blogger: Prof. Terence Tao, Fields Medalist.
Blogger: Prof. Timothy W. Gowers, Fields Medalist.
(Group blog) Founders: Alexander Ellis (Harvard), Sam Lewallen (Princeton), Yan Zhang (Harvard).
AMS Graduate Student Blog
Editor-in-Chief: Kareem Carr.
Blogger: Nestor Guillen,Graduate from University of Texas.
Women and mathematics
Blogger: S. Paycha, Dusanka Perisic, Marjo Lipponen.
Division by Zero
Blogger: Dave Richeson, Associate Professor of Mathematics, Department of Mathematics and Computer Science, Dickinson College.
Geometry and the imagination
Blogger: Danny Calegari,Professor of Mathematics,
Department of Mathematics,
California Institute of Technology
I Woke Up In A Strange Place
Blogger: Ioannis Parissis,Mathematics Dept of IST.
A Day in the Life of a Wild Positron
Blogger: Student, Princeton University.
392C: Geometric Group Theory
Blogger: Henry Wilton, Univ of Texas (Presently at Univ College, London).
Virtual Math Tutor
Tanya Khovanova’s Math Blog
The American Mathematical Monthly