I came across this research group at Stanford on the interwebs recently called SoundWIRE. They have a lot of interesting projects, and one of which, called Jacktrip, is a program that, once installed, allows you to "jam" with friends via the internet. This software is all open source and free, but I've never used it myself. Hear good things from other communities of musicians online I am a part of.

Just thought I'd mention it smile


Cheers,
Deryk