Last week, in a suit brought by Public Citizen on behalf of Stanley Kutler, the American Historical Association, the American Society for Legal History, the Organization of American Historians and the Society of American Archivists, a federal district judge ordered the release of the grand jury testimony of Richard Nixon in 1975. The press release is here; Allison Zieve, the Public Citizen lawyer who litigated the matter, discusses the case here.
Another account is here.
Public Citizen has won the release of other grand jury testimony, perhaps most notably that of Alger Hiss. Please comment if you can think of other grand jury testimony that might possess sufficient historical significance under this line of cases.