Salsa is a tiny package for playing sound on one computer, and hearing it on another. I use it in my livingroom to play music on my wireless laptop, and hear it through my home stereo. If you have a media center PC, you may find Salsa handy.
Salsa works by directing ALSA to dump PCM data to a FIFO (named pipe). The salsad daemon forwards any data written to the FIFO to a remote host over a weakly encrypted ssh tunnel. In this way, Salsa is able to work with any existing audio application. ssh is used so that remote authentication may be automated via RSA keys. The aplay player is invoked on the remote host to play the PCM stream, and there you have it.
The latest stable release is 0.2. The README may be viewed here.