I produce resources for whatever modules I teach. I have yet to teach M1-M4 (given my stats specialism) and have only taught M1 in a tutorial capacity. My school does not teach Decision Maths. Sorry!
Different teachers with an online presence often have a different 'niche'. Sites like www.examsolutions.net and www.corbettmaths.com already do the video thing quite well (with very gigantic libraries!). My 'niche' as a resources website (if I have one) is ready-to-go full resource sets for teaching, revision notes, and material for higher ability students (as well as the upcoming homework platform). It's unlikely I will go down the video route anytime soon.
I used to regularly speak at the Maths In Action events at the Institute of Education in London for The Training Partnership, on revision technique for A Level mathematics students. You can find the slides here. As a full-time teacher I can't otherwise take time off, but please contact me if you wish to discuss anything regarding this.