Skype.com. Pretty good service, but I recently found out that I cannot use SkypeToGo to call China. I didn’t even know about SkypeToGo until recently. I was looking at other of the services that came with my subscription and I saw it. Basically, I can use my cellphone to call a US number. Then I am connected to my Skype account. From there I can choose one of 6 speed dial numbers (which I set online), or I can manually enter country-code and phone number.
But China is one of about 15 countries that SkypeToGo is not allowed to call (due to common fraud, abuse, or whatever). I can’t use my cellphone to call WeiLing when I’m on campus, or away from home, etc. But not that big of a deal. In general, I’m pleased with the Skype service and still use it as I did before I learned of SkypeToGo. Blah. 
In short: Skype works for me. SkypeToGo does not. Sorry if I wasn’t clear.
