JackTrip 
JackTrip is a Linux and Mac OS X-based system used for multi-machine network performance over the Internet. It supports any number of channels (as many as the computer/network can handle) of bidirectional, high quality, uncompressed audio signal steaming.
You can use it between any combination of Linux and Mac OS X (i.e., one end using Linux can connect to the other using Mac OS X).
It is currently being developed and actively tested at CCRMA by the SoundWIRE group.
Links
- Preliminary Documentation and API.
- Subscribe to the Mailing List.
Related Software
JMess: A utility to save your audio connections (mess).