Prof. Douglas B. West mantains a comprehensive List to Combinatorial Conferences.
Prof. Igor Pak has a Collection of Combinatorics Videos.
Mathematics Subject Classification 2020 from MathSciNet.
Spectra - The Association for LGBT Mathematicians
Online Latex Editor - Overleaf
Dr. Jonathan Noel has a wonderful advise page to students and early career researchers in discrete mathematics.
Chao Xu's Advice (in Chinese)