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