FreeRinger

Freeringer is a web-based
flash application which allows users to make free internet calls from their computer
to fixed line phones or cell phones in more than 30 countries worldwide. Just like iCall and Evaphone you don't require to download any software but you need to register an account first. Once you're logged in, you will see a dial-pad and your Talkster roster right to it. Upon first connection there will be only one contact Echo Test Call, which is helpful to test your audio subsystem and network capabilities. After you confirm usage of your microphone, you will be connected to a voice prompt guiding you through echo test service.

http://www.freeringer.biz/