I quite often fly on VATSIM with my cousin and can talk to him in text but I believe there is a way of actually talking to him on voice using the Squawkbox add on - can anybody tell me how?
Not sure about using Squawkbox but I know you can use Team Speak; its a very good way to talk to people. I have used it in the past for Counter Strike
I believe that all it takes to set up a private voice channel on VATSIM (after you configure your mic that is), is to simply go into the SquawkBox menu -> private voice -> join channel. Simply type in a name and have a buddy do the same. As I recall, you don't have to do anything special to get this channel. I very well could be wrong though!
Oh, and don't forget: the push to talk keys for private voice and for ATC communication are different! Make sure you keep them straight, or ATC could get a little upset .