MadPenguin.org looked at SIP and Skype
Over the past few months, I have found myself conflicted as I have time and again found myself perplexed in an effort to locate a good quality VoIP option for my Linux box. It's been my experience that many Linux purists will expect you to be using some sort of SIP soft phone, and frankly balk at the very idea of running Skype on their systems. After doing a little research, I’m beginning to understand why.SIP vs. Skype: Making the "Open" Choice