Team Sound
I use "Team Sound", you can find it at download.com .
It´s really good, you can host different "Channels/freq.", so if you are many players in you team, you can have one defender channel and one Attacker channel or what ever you want.
Ant you can talk to both channels and choose witch one you want to listen to. And you masters all this by key combinations you choose your self.
Sinece we´re only 2 members in my team, we just have one channel.
Ofcource threre is som delay, like 0.5 - 1 sec, so you can´t realy just scream "enemy behind you!!", couse he will recive to late.
But it´s REALLY good anyway, takes the teamwork to another level.
If you are interested in trying it our, contact me vie email and we can play a match against bot or something if you want.
http://pistvaktarna.cjb.net
Reagards
Tobias