There is an informative glimpse into the recent work of Mavis Staples over at Living In Stereo. Go Listen. Tell em what you think. Buy what you love so you love what you've bought.
My favourite Mavis Staples surprise was when I bought Natalie Merchant's Motherland album in 2001.
Mavis Staples sings emotive harmony vocals on two tracks. My favourite is
there are other versions of Saint Judas (albeit without the powerhouse Mavis Staples) at Natalies Exhibits page which included verses considered (by whom?) too strong for the album release.