Improve Your Backgammon
Chris Bray Backgammon
https://www.chrisbraybackgammon.com/
Backgammon To Win is recommended for beginners and those wishing to deepen their understanding of backgammon theory.
The “Wind” books are collections of articles from the Independent. Each article is a problem discussed on one page, so you can read bite size.
The Position of the Day on the website has shorter discussions.
https://www.chrisbraybackgammon.com/position-of-the-day/
The Gammon Press
Bill Robertie’s blog has many, excellent short articles.
Backgammon Galore!
Free
Gammon Village
https://www.gammonvillage.com/backgammon/magazine/
Subscription
BG Online
https://www.bgonline.org/forums/
Free lively discussion board at an advanced level
US Backgammon Federation
Not restricted to US citizens