Webdav maybe?

Many recent OSes support it in some fashion natively, there is a cli client (cadaver), and it runs fine over ssl.

It is rather heavyweight and slow though, and doesn't offer quite the range of things as some ftp servers (ratios, etc). That is likely just due to the lack of popularity and the few options for servers.

SFTP (which you discounted) is probably a better option in many cases though.