Roger McGuinn is best known as a member of the Byrds. The Byrds helped expand popular music by fusing folk music with rock.
Roger McGuinn's web site has a section called "Folk Den" which features free MP3 downloads of McGuinn performing old folk songs. The same page includes links to McGuinn's recordings of other classic songs sinch as Home on the Range, I Heard the Bells on Christmas Day, and The Star Spangled Banner.