Other, not too difficult to use methods:
Make a torrent and send them the torrent file. I recommend using
uTorrent. You'll be sharing the file on your computer through uTorrent. They'll download it directly from you with uTorrent on their end using the torrent file you send them.
Set up an FTP server. Lots of software out there for doing this and is pretty easy. If you're behind a firewall then you'll need to setup port forwarding so they can "see" your FTP server.