Open source identity: PulseAudio creator Lennart Poettering (CIO)

Yep, PA does that nicely. It can even do it automagically, if your hardware and
drivers correctly label stuff and report jack sensing, I gather. PA can also
transparently redirect your sound to other machines on the network, on the fly.
With zero-conf auto-detection of other PA servers too.

The extra layer of volume controls is quite infuriating though - you can get very
strange and unwanted behaviour when you use the master volume in the
presence of multiple sound sources. Anyway...