Harvard University has made offers to Martha Nussbaum (moral and political philosophy, ancient philosophy) and Cass Sunstein (constitutional, administrative, and environmental law), both on the faculty at the University of Chicago Law School (and each jointly appointed to other units at Chicago). Nussbaum's appointment at Harvard would be in at least Law and Classics; Sunstein's at least in Law. Their departure would obviously be a major blow to the University of Chicago Law School.
UPDATE: As various readers informed me, Harvard Law School has also had an offer outstanding for quite awhile to David Weisbach (tax) at Chicago. In addition, Chicago's Adrian Vermeule (constitutional law) has been visiting at Harvard, and is under consideration there for permanent appointment. Whether any of these folks actually go to Harvard remains, of course, to be seen.