Utah Phillips, 1935-2008.
They are playing some archived interviews with him on Democracy Now! this morning, but I wasn't able to find a live link for it as of 6:15am (PST).
I had the very good fortune to get to hear him (and Rosalie Sorrels) in Santa Cruz in 1994.
Travel well, Grand Duke of Hobos.
(Here are some more linkages. To his website, an SF Chronicle piece, and an interview from 2003).