MATHLINKS
Mathematics on WWW/
NBHM/
Millennium Problems/
Hilbert's 23 Mathematical Problems/Mathforum
Mathlinks for School children
International Mathematical Olympiad(IMO)/
IMO problems(tex and html)/
Indian Mathematical Olympiad/
Art of problem solving/
USA Mathematical Talent Search/
History
Index of Ancient Indian mathematics/The History of Mathematics(by David R. Wilkins, Trinity College, Dublin)