[MrBouzouki]

The MusicNotes Blog has some great articles. I've recently be reading all about Secondary Dominants that is very interesting.

https://www.musicnotes.com/now/musictheory/introduction-to-secondary-dominants/

There is also a great on on memorising modes

https://www.musicnotes.com/now/tips/tips-and-tricks-to-memorize-musical-modes/

I quite like the padMIL formula and the simple fact of remembering

Ionian – Major Scale
Lydian – Major Scale with a raised 4th scale degree
Mixolydian – Major Scale with a lowered 7th scale degree
Aeolian – Minor Scale
Phrygian – Minor Scale with a lowered 2nd scale degree
Dorian – Minor Scale with a raised 6th scale degree

The main landing page is here :-

https://www.musicnotes.com/now/category/musictheory/