[all variants] How can I access my shared folders over the internet?

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http://ubuntuforums.org – I've got my music folder shared via the "sharing" tab in nautilus folder properties, and I have no trouble accessing it from another computer on my home network. What I want to do is to let my friends access this remotely. What's the easiest way to do this? I tried setting up an SSH server, and even managed to forward the ports, but it shares all my folders, and I only want to share one. (HowTos)