Wikipedia
GMInsideNews
GM Inside News (abbreviated GMI) is an Internet Forum focused on General Motors, its brands and products.
While truly "inside" news is a rarity on this site, when GMI does get a "scoop" bigger and more established publications have been known to use the popular site as a source. As of recent GMI shows info from all car makers, not just general motors.
As of February, 2012 GM Inside News has over 55,000 members and 2,000,000 posts.