Here are a selection of resources which I find useful
Muay Thai
Websites
Muay Thai Pros – Clean, easy to navigate website about Muay Thai with lots of information
YouTube
fightTIPS – First youtuber I found when trying to search for Muay Thai technique demonstrations
Sean Fagan – Another YouTuber with useful technique demonstrations, also the owner of Muay Thai Guy
General Fitness
NHS Fitness Studio – A good place for people just getting started in exercise
Darebee – Free Fitness, Forever, For Everyone