VOIP and iptables dodgies :)

Hey guys.

I have two questions ( i hope that's not too selfish :) ).

Firstly, have any of you had any experience with VOIP. i know that tpg have 
just started offereing it in combination with their broadband plans etc. Just 
wondering what some (real peoples) experiences are. quality? value? etc. any 
ideas.

Secondly, i'm a student at the university of melbourne. and to use their 
proxies, you have to set those manually (fair enough). i was wondering, is 
there a way to make the server (i assume using iptables) pretend it is the 
university server whilst i am at home? ie pretend to be proxy.university etc 
for internally generated packets?

thanks for the ideas,

coldflame