I love Fresh Air's "rock historian" Ed Ward. He really nails it every time out - even when he covers stuff I know a lot about I learn something, and I'm never lost when he covers something I've never heard of.
He's had two great Fresh Air segments recently. This one covered the early days of Sly Stone (aka Sylvester Stewart), when Stone was still best known as a radio DJ and record producer. It even includes some rock records he produced (I had no idea, and I couldn't be a bigger fan).
This one covered another early-70s soul legend, Syl Johnson. I had no idea his career stretched so far back before his days working with Willie Mitchell, as the bluesier Al Greene.