Also, I have a friend that swears by using C3, which is some supposedly new and coming voice client?
He says the benefit is there is no need to rent servers, no limit to people in a room, and ability to create subchannels on the fly. The quality is also comparable to / better than skype.
and he gave me this link xD
http://www.downloadc3.com/guilds-and-clans/
Dunno, maybe this is pretty good? They claim its also designed for gaming so that seems like a plus!