Sometime back I found an official Neil Young anti-war blog. I was impressed for a moment, but it appeared that he did not himself blog there, though it was "officially" his. (And for some reason, the most recent post is dated May 2007.)
More recently I came across David Knopfler's very lefty blog. David is no Mark, having extricated himself from Dire Straits after an early Communiqué, but his music (available at his myspace page) seems pretty listenable.
I came across David's myspace page by way of Anjani's. David is the brother and one-time backing guitarist of a well-known musician with a sandpapery voice; Anjani is the girlfriend and long-time backing singer of another musician with a gruff (or, as he puts it, "golden") voice, Leonard Cohen. More to the point, Anjani has recently released a fine album, Blue Alert, that combines Cohen's moody lyrics with her own tunes and musical arrangements: minimalistic jazz, mostly just her piano, a relief from Cohen's own recent pop-synth arrangements. Outstanding stuff. Other reviewers have said that she sounds like a female Cohen or that Cohen's voice (though it doesn't actually appear) "permeates the album like smoke", but I think she brings a quite different dimension to his words. (Compare, for instance, this version of "Nightingale" with the one on "Dear Heather".)
I don't know whether Anjani blogs, but she apparently reads and posts to them, actually getting into an amusing discussion with a reviewer who expressed his desire to bed her (simultaneously with two other female singers). LC himself chips in at one point.
I look forward to more from LC and Anjani. More music I mean, but the blog exchange was fun to read, too.