Here's a VOIP service I think that's not been mentioned in this thread. I use it with my mobile or landlines to call overseas or long distance calls within Malaysia as it's cheaper than telco rates and equivalent to Skypeout rates.
It's Minowireless
The advantages are

1) You do not need a broadband or 3G/HSPDA connection. Even a GPRS data connection will do which will tell the Mino servers to connect the destination phone with your phone. The data usage is miniscule - something like 1-2 Kb
2) You receive an incoming call in your mobile phone (or landline if you choose) so there are no telco call charges. It's basically similar to a call back service.
3) They have a Java client which works with alot of phones (Mino Mobile). There's also support for Palm and WM phones. This makes Minowireless truly mobile. You can also initiate the calls from your Internet connected PC or mobile phone's Wap browser.
4) They accept Paypal payments (important for me)
5) Call quality is pretty good, minimal latency. About as good as Skypeout.

This post has been edited by palmjack: Nov 1 2007, 07:25 AM

Well main advantage is you don't need broadband.