I've always loved David Bowie's "Wild Is the Wind." A few months ago I discovered that it's a cover of a song originally sung by Johnny Mathis. Then some time after that, I discovered that Bowie's version is a tribute to Nina Simone's version.

I could have learned this by reading the Wikipedia entry, but I learned it the long way:

I heard the Johnny Mathis version at my favorite English teahouse restaurant (The English Rose in San Carlos).

I found the Nina Simone version by listening to a Coverville podcast on Kurt Weill which includes Simone's rendition of "Pirate Jenny." I proceeded to dig around on iTunes for her other stuff and discovered several versions of "Wild Is the Wind." (I have two versions, one from Nina Simone Live at Town Hall and another live version from Four Women: The Complete Nina Simone on Philips Recordings.)