A passworded zip file would probably be my choice, easy enough to open at the other end even for technologically illiterate people, and doesn't take anything fancy to make.
Pretty sure they're zipping for the encryption, not the compression.
edit: the way I'd solve the rest is just by using a torrent magnet link. The problem with that is that you might have to teach someone how to open a port for UDP traffic, but after they've done it, sending files of any size to them becomes trivial.