I copy SQL Server backups over the Internet. I have two remote servers connected using a (paid for) LogMeIn Hamachi2 Peer-to-Peer VPN. I then transfer the files over the VPN using rsync (a Linux application not used much in the Windows world but is available as part of the Cygwin install). No need to compress the backups - just let rsync (client/server) work out which blocks have changed and it will only transmit the differences.

Its all command line stuff so create a script and launch it from another step in your SQL backup job following the actual backup.