Youtube
From A complete guide to Super Metroid speedrunning
Eterniseddragon - Tons of unique clips, mostly involving obscure and/or complex item interactions (and tons of romhack/category playthroughs)
Dessyreqt - Various theories, techniques, and tutorials
Twocat - Advanced room strategies
Smokey - Various any% strategies and comparisons
Super Metroid FTP(Japan) - Random (mostly tool-assisted) clips
Catnap222 - Discoveries made in the early days