Hi, I'm on WinXP and I use Skype for a long time, and the sound quality is amazing; I just discovered vSkype, a video plugin for Skype. It can handle up to 200 users simultaneously, and you can also share your desktop or just a part of your desktop (i.e. a window). Skype is available for multiple OS (Win, Mac, Linux, ...) but unfortunately vSkype is currently only available for Win2k+.
Greg.
