I thought RSS Bandit may have revealed something early but it was just the number of unread posts in the Windows category...
UPDATE 2008-08-16: Just found this Windows 7 blog from Microsoft;
Welcome to Engineering Windows 7
Welcome to our first post on a new blog from Microsoft - the Engineering Windows 7 blog, or E7 for short. E7 is hosted by the two senior engineering managers for the Windows 7 product, Jon DeVaan and Steven Sinofsky. Jon and Steven, along with members of the engineering team will post, comment, and participate in this blog.
via IE Blog