Seems too good to be true, right? But It works!
http://evaphone.com/ lets you do that. Call any mobile or landline in any part of the world from any part of the world for free. Unlike Skype, it is free and is browser based. No call charges, no registration, no installation-nothing whatsoever. Just go to the website and enter the number prefixed by the country code and area code, if any.
Evaphone is a web2.0 website where all calls are currently advertisements supported. Since the website is pretty new it doesn’t have any ads besides the one which are there at the sides!. It does have a very irritating video which plays before every call though. HAPPY CALLING!
PS: Many websites like this come up and then go into oblivion. I hope this one doesn’t.