Blowing the Blues: A History of Blues Harmonica by Various Artists
this is a fantastic 3 cd set on the history of blues harmonica - tracklisting and samples here
the first 2 cds are absolute gems with the legends of pre war harp such as Noah Lewis, Jaybird Coleman and Jazz Gillum. The 2nd cd deals with the golden age if you like - the Sonny Boys, Little Walter, Big Walter - you know them - includes some great harp work. Cd 3 is a little less indespensible but who knows - maybe it'll grow on me.