Документация:
https://www.opengl.org/sdk/docs/
https://www.opengl.org/wiki/Main_Page
https://www.opengl.org/registry/
http://docs.gl/
https://github.com/g-truc/ogl-samples
Тьюториалы:
http://www.learnopengl.com/ ( Переводы на Хабре )
https://code.google.com/p/gl33lessons/
https://triplepointfive.github.io/ogltutor/index.html
http://www.opengl-tutorial.org/ru/beginners-tutorials/
Полезные ссылки:
http://tfc.duke.free.fr/
http://tfpsly.free.fr/bookmarks.html
https://github.com/eug/awesome-opengl
https://www.youtube.com/user/BSVino/playlists
https://www.youtube.com/user/thebennybox/playlists
https://habr.com/post/248153/ (Краткий курс по КГ)
https://www.shadertoy.com/
http://www.andersriggelsen.dk/glblendfunc.php
Архив:
https://arhivach.ng/thread/28624/
https://arhivach.ng/thread/47586/
https://arhivach.ng/thread/64117/
https://arhivach.ng/thread/192404/
https://arhivach.ng/thread/250601/