One of my favourite songs of all time is the Velvet Underground's 'Femme Fatale'. Lately I've been rocking the recently discovered acetate pressing of the original Scepter Studio recording sessions for The Velvet Underground and Nico. The sound quality is actually decent, and I'm hooked on the fuller backing vocals and more prominent percussion.
If you haven't heard the story of how a dude from Montreal paid 75 cents for a record that ultimately sold for over $25,000 then read it here (in the comments section).
If you want to grab all nine tracks from the "lost" Scepter sessions in mp3 format, they're available here. Some are completely different takes than the eventual album versions, and all are different mixes.
The Velvet Underground - Femme Fatale (album version)