I was gratified at my guitar lesson yesterday, when after showing my teacher a chord progression I liked, he improved it a bit and said he might have to steal it. In my efforts to add B Major (and other A-major shape barre chords) to my repertoire, I started playing B->D->E->G. He explained to me that these chords sort of fit together because I was playing two chords from Emin and two from E. If I remember correctly, he swapped out the D for an A (so B->A->E->G) keeping three chords in E major. And then he hummed a nice melody over it.
If you are musically inclined, give them a whirl. I suppose there are other similar sounding sequences combining other major and minor keys.
And now I'm really looking forward to this weekend, when we may have a little jam session. I need to get a bit better on some twelve bar blues progressions, working on my 7th chords.
Ruthie, you should play some blues.