PulseAudio is a cool audio system for Linux, which allows easy audio networking. It means that instead of playing sound, your computer might send its audio stream over the network to a PulseAudio server, which will output the stream on its loud speakers.PaWebGui is an opensource (GNU/GPL) web-based GUI interface for PulseAudio. I wrote it, because I needed to control my central audio computer remotely. It's a cgi program, which requires a web server running on the PulseAudio server machine. I would recommend Grumpy as a http server, for the simple reason that it's the only server I tested PaWebGui with (plus, Grumpy is lightweight and easy to set up). PaWebGui allows you to set various settings of the PulseAudio server, like a per-application volume, redirection of sound programs to different sound cards, etc...
If you would like to see what PaWebGui looks like, feel free to check out my screenshots!