WFMU podcasts its Downtown Soulville show, a solid hour of vintage soul 45s both popular and obscure. Check Mister Fine Wine's playlist page and podcast link
here.
Also, once a month another soul DJ on FMU subs for Fine Wine. His RealAudio archives can be found
here.
As to specific artists, I like some of the Detroit Emeralds' work, particularly "Feel the Need in Me." Also, the original soul version of "Don't Leave Me This Way" by Harold Melvin and the Blue Notes is very nice.