One that I found the Electric Light Orchestra LOVES, (as do I) is major, major 7th, seventh, eg. "Can't get It Out Of My Head" G - Gmaj7 -G7. GUEST, Jim Croce uses the Dm - Dmin maj7 - Dm7 - Dm6 in "Time In A Bottle". I agree, you never realize how much you've heard it and not noticed. And what a great progression it is, too!