Playing your music over the internet

TwonkyVision

My NAS uses TwonkyVision as a UPnP server.

TwonkyVision also offers a web interface (http://IP_Nas:9000/webbrowse)

If you use port forwarding on your router, you can browse and play your music over the internet using this interface.

Windows 7

A new feature is too access your media at home over the internet.
You need a Windows Live ID to do so.

A setup guide can be found here: http://www.neowin.net/news/main/09/03/12/windows-media-player-internet-access-to-home-media

Vista

Vista offers the option to remotely access your media using VPN (Virtual Private Network).

A virtual private network (VPN) is a computer network that is implemented in an additional software layer (overlay) on top of an existing larger network for the purpose of creating a private scope of computer communications or providing a secure extension of a private network into an insecure network such as the Internet.
http://en.wikipedia.org/wiki/Virtual_private_network

A setup guide can be found here: http://theillustratednetwork.mvps.org/Vista/PPTP/PPTPVPN.html