Want a low-powered music server for your home? You can use your Raspberry Pi and the RasPod software.
RasPod turns your Raspberry Pi into a wireless music server and than allows you to tap into it using any device that supports Wi-Fi and has a web browser. All you'll need is a Raspberry Pi, a wireless router, and a stereo.
It's not exactly the prettiest music player out there, but it's fast, and doesn't suck up a lot of juice. If you combine it with Spotify and Pandora, you'll have a fairly complete little system. You can find the full installation instructions over at GitHub.