Some links I find interesting

arxiv.org

mathstackexchange

mathoverflow

Possible list of best online maths videos

Life and travel in 4D

Pythagoras disproved

Undergrdauate Mathematics Journals

Singapore Maths Cathy Duffy Reviews  Teach your kids mathematics

The two culture of mathematics

Advice for research students

Maths Jokes

Write your first maths paper in five minutes 

Mathgen paper