I have a friend going to D.C. next month and we checked with the office of my Member of Congress (Peter Deutsch), who verified the information in letiole's post - and that there is no anticipated resumption of either the Congresional or the General tours anytime soon (maybe 20.01.2005)??

The great advantage to the suspended Congressional Tours was that they had a fixed start time (08:00 - avoiding the long general queue) and often included a public room that was not on the general tour.

The FBI Tour (including the quite interesting Crime Lab) is also suspended, although the stated reason is for "remodeling" (I guess a few nekkid statues still need coverings)

Unfortunately the Rotunda of the National Archives (housing the Charters of Freedom - Declaration of Independence, Constitution and Bill of Rights) is closed for the completion of its remodeling and will open on 18 September (since you are from the UK that may be just as well)