So glad I found this thread! I've already googled many of your favorites to my delight.
"Killing The Blues" is one of my new favorites. Many covers; but I still like Plant & Krauss from Raising Sand.
Great to see some love for Joan Osborne. She is a great talent.
I'll throw out a few.
"Summertime" Big Brother & The Holding Company The Zombies also do a fresh cover.
Anything by Dusty Springfield - she pretty much owns anything she covered.
"Hey Joe" -so many good versions. Hendrix, of course, but Black Cat Bone may be the best.
"Morning Dew" - I have 15 versions. Long John Baldry is my #1, the version from his self titled EMI LP.
All of Linda Ronstadt's covers of Karla Bonoff and Gary White. Respectively my favorites are "Someone to Lay Down Beside Me" and "Long, Long Time".
The Siklie's version of the Beatles "You've Got To Hide Your Love Away"
"Down by the River" covered by the Indigo Girls.
More later. I can't help myself!