There has been some press in the voip space over the past few days about the new Vivox SLim application.
Linden Labs and Vivox partnered to create SLim which is a discrete VOIP client that is meant to run alongside the Second Life viewer allowing it to communicate voice calls with others not necessarily running the Second Life application.
Vivox isn't really that big a deal, Mexuar implemented a 168k java applet using the open source Asterisk platform into Second Life about 18 months ago.
It enabled voice calls in both a many to many 'open voice' conference room but also the ability to make 'real world calls' onto the pstn network either outbound or even inbound using the Asterisk servers PRI's or Voip channels.
At one stage there was a mock up of a virtual cell phone you could use in Second Life to make calls or link inbound calls to your real world cell phone as well.