I am currently in the process of migrating several dozen sites between two servers. I tried using scp command to copy the sites over however scp is a very slow command when transferring many small files.
Using this method effectively sends the compressed tarball to the terminal. You then pipe that into an ssh session which is running the extract version of the previous tar function along with the change directory argument. This, essentially, sends the compressed tarball into a decompression process at the other end over a secure ssh "pipe".
The result is a pretty quick file transfer which - as the data is being sent in a compressed GZIP form (of BZip2 if you replace the z with a j in the tar functions) you save on bandwidth too.
Here an an example of how to do this, assuming you are in (for example)
/var/www/html/ and the website you want to transfer is the folder
tar czf - www.example.com/ | ssh firstname.lastname@example.org tar xzf - -C ~/
This will send the entire www.example.com folder over to the home folder on your target server in compressed form over and encrypted connection.