My brother in Europe bought a computer recently, and we used MSN Messenger a few times to talk (typing). He got a mic today, and we did voice-chat. It works just like a phone! I didn't think it would work too good since he's on dial-up, but it worked perfectly. This is gonna save me a lotta $, lol.
Second Skype. I use MSN a lot and I think skype is way better audio wise. Also, for some reason, I can never get the audio to work at the same time as the webcam in MSN - it seems it makes me choose one or the other.
Using the phone is cheaper or at least more comfortable if he's in Germany. I pay about $.02 per minute if I call somebody in the US (even on mobile) and I have the comfort of calling without using my machine.