As more and more is digitized and new developments are probably digital only the Library of Congress has seen the need to develop a method to transfer content between computers. They developed a 'digital bag', about an equivalent of the physical envelop, with a few extra's needed for the digital content. Of course the bag is also digital.
There is a video presentation
here.
When looking around you can also look at the issue of personal archiving (in a digital world)
here.
Cheers
Kees