I’m a big fan of Southern Soul, particularly the Memphis and Muscle Shoals forms. But because there was so much fantastic music from those two areas, it’s easy to get stuck listening to Stax, Fame, Atlantic and Hi artists. Even their duds are better than most of the competition. 
This year-old Southern soul collection from Ace Records is killer.But I’d encourage any fans of R&B and soul of that era to check out “Take Me to the River: A Southern Soul Story 1961-1977.”
It’s an absolutely brilliant three-CD set from Ace Records that collects 75 songs from artists and labels big and small. There's Aretha, Wilson Pickett, Percy Sledge, William Bell, etc., but the emphasis is on the little-known tunes or one-hit wonders. Some of the production leaves a bit to desired, but the performances are top notch top to bottom.
To top it off, the packaging is superb. The CDs come in a similar-sized hardcover book that features full glossy photos and stories behind each song.
It's pricey (I paid $48, but notice Amazon's price is now $60) but highly recommend it for fans of Southern soul, classic R&B and the roots of rock.