Windows/Mac/iOS/Android: Audiogalaxy, the surprisingly simple app for streaming your own music between computers and smartphones (surprising in how rare that is, at least) is out of beta and open for registration. Download it, activate it, and listen to your tunes anywhere.
As it did during the beta test, Audiogalaxy makes it easy on the installer. After grabbing the Windows or Mac desktop software, the app automatically finds your music and offers it up to your Audiogalaxy library — just the listings, though, and you can fine-tune that. Install the client on your iOS or Android device, sign in (through an Audiogalaxy account or Facebook), and you've simply got all your music available through a net connection. You can also stream from computer to computer, if you'd like. There are playlists and other doodads available, and reverse iTunes playlist syncing, if you'd like that.
Audiogalaxy is a free download for Windows, Mac, iOS and Android devices. You can read up on the history of Audiogalaxy, from its days in the same bucket as Napster to its modern, pared-down implementation, on the Audiogalaxy blog.