Practice Pal
Practice Pal is probably more for music tutors than teachers. You can setup timetables that emails reminders and you can also setup payment for your lessons. A very good, specific product that you can run on Freemium.
Feel Good Friday
Sign your class/school up for Feel Good Friday, a weekly streamed music lesson. It may inspire more awesome musicians like these (see video).
Sonic Pi
Sonic Pi is a download that I would absolutely get on any school music computers. It lets students create music 'digitally'... see the video.
Websites
Classroom 200
Classroom 200 has a vast array of lesson resources covering all sorts of genres. It is genuinely very impressive. Absolutely get yourself an account and have a scroll through them to see if something catches your eye (I was very excited to spot LOTR, my fav).
pBuzz Primary
pBuzz, creaters of a whole new instrument, here offer you free SoWs for Primary including all lesson resources.
Apps
Big Ear
The Big Ear app is a fun way to learn how music works. Compose popular songs through puzzles and even write your own!