Sneakernet is an old term meaning the process of downloading software, mail, whatever on machine a, connected to a network, then creating some sort of physical media (paper, floppy, tape, CDROM, DVD, etc.) which is then hand-carried to the other machine and loaded there.
In the twenty-first century, it often involves sending entire servers through postal mail: http://www.acmqueue.com/modules.php?name=Content&pa=showpage&pid=43