One thing not mentioned in my list is the addition of video to Skype. But vide is now built in to Skype for Windows and there are additional video options available for Skype, so that is a topic for another article and my next book "Video Conferencing over IP" by Syngress Press due out in June 2006.
So without any further ado, Here's the list of my favorite Skype add-ons:
1. VoSky (Formerly Actiontec) Internet Phone Wizard (IPW)