It seems that Rearview Mirror will be a collection of rare studio tracks, plus a new song, "Run Diana Run" and of course they're including "American Pie" on it (which I don't think is necessary but whatever).
The new track is supposedly a "sneak peek" at Don's album of new material, called Addicted to Black (the title song is GREAT, he played it at the concert), supposed to come out in 2006, as is his official biography. Hopefully this will all materialize! I'm excited! =]