I'm going to do something quite unorthodox now, but what I just came across is so amazing I simply have to share it with everyone, everywhere.
I just stumbled upon a VOIP program called Mumble. It's amazing. I sincerely believe that if the development of this project continues, this program will dominate the gaming scene completely.
It's completely free, AND open, which means that you won't be having any issues whatsoever with licensing problems like you do with Ventrilo, nor will you have annoying setup screens and delayed sound as you do with TeamSpeak 2. Mumble is simply amazing. It's very easy to setup, the sound quality is extremely good and it even supports 3D sounds in-game for a bunch of games.
If you are an avid gamer, or if you just happen to enjoy chatting with your friends over Ventrilo/TeamSpeak2, I strongly suggest you to give it a go. Trust me, you won't regret it.