Helpful general links:
USA Pickleball
Rules of Pickleball
PickleMall
Pickleball.com
Pickleballbrackets.com
DUPR

Good educational/training video resources:
ThatPickleballGuy - Kyle Koszuta produces very entertaining and educational videos. See his YouTube channel here.
He has a great video explaining the basic rules and how to score doubles Pickleball.

Briones Pickleball - Jordan Briones is one of the OGs of pickleball educational content. His YouTube channel has lots of great videos.

John Cincola - Playing pro who has some great educational and drilling videos. See his YouTube channel.

Simone Jardim - The OG woman pro—she was #1 in the world for a long time and has a lot of good drilling videos. Her YouTube channel is here.

Paddle reviewers:
John Kew - very in-depth and technical reviews of paddles.

The Pickleball Studio - great paddle reviews and entertaining podcasts.