Are we counting collaborations? She sang backup on some songs on Mark Lanegan's Bubblegum album, sang some of the Desert Sessions 9-10 songs (don't forget the Crawl Home single, with a Desert Sessions cover of Whores Hustle), and sang on a Moonshake album. She also did Green Eyes, Love Too Soon and Featherhead with Pascal Comelade. I think the Gordon Gano and John Parish tracks have been listed here already.
My favorite is Just A Working Girl from the Moonshake album.