I had forgotten about the name for a while until, the other day, when it came up again in a recent episode of a podcast I was listening to. So I decided to do some research. In short, he was an American actor and writer who may have been best known for his monologues. I've posted the two that I've watched so far. Both originally aired on HBO; one in 1988 and the other in 1996 (directed by Steven Soderbergh).
It's difficult to know where to start. I really enjoyed these two monologues - everything from the economic/minimal set, the on and off-stage reenactments (some reminiscent of something like Drunk History), and just his style of writing in general.
All this to say, I can definitely see why people would assume Spalding Gray might have been a proponent of podcasting.