Beginner
Learn HTML in 12 Minutes (www.youtube.com)
HTML Best Practices (github.com)
How to Use the HTML5 Sectioning Elements (blog.teamtreehouse.com)
HTML Content (www.codecademy.com)
Organizing HTML & CSS (www.codecademy.com)
Front End Interview Handbook (github.com)
Learn HTML (www.codecademy.com)
Marksheet (marksheet.io)
HTML Fundamentals (www.codecademy.com)
HTML Beginner Tutorial (htmldog.com)
w3schools (www.w3schools.com)
Intermediate
HTML Intermediate Tutorial (htmldog.com)
Advanced
HTML Advanced Tutorial (htmldog.com)