I'll have to do some digging to come up with a source, but I remember reading that there is no published no flaps landing speed for the 747 because the flaps are gravity driven for the first notch or so, and that the touchdown speeds with no flaps would blow out all the tires on the main landing gear.
"Few airlines offer their pilots procedures for flaps-up landings in a 747, according to one pilot. Their manuals, however, provide data allowing crews to determine how much runway will be needed. They know what to expect: The aircraft will approach as slowly as possible, but will still be faster than the design limit for the tires. Most of the tires will fail during the touchdown. One airline has pilots practice making no-flaps approaches, but the training is never carried through to touchdown.
Given the available backup systems on board, it is unlikely a 747's flaps would ever fail to come down. For example, there are ways to substitute the use of electric motors for lost hydraulic power. In addition, when alternate flap-control measures are used, all leading edge flaps extend simultaneously as soon as the flap handle is moved from its Up detent. That lowers stall speeds by 20 knots and approach speeds, while still faster than normal, are then within tire limits."
"The Flap About Flaps"
, Alton K. Marsh. AOPA Pilot Magazine, August 2004.
[Edited 2007-10-26 15:18:52]