One of the best ways to make calls to phones from a PC is to use Google Voice. Some other services that allow users to make phone calls from their PCs are Rebtel, Skype, and Nimbuzz.
Google users may use Google Voice to make calls to phones in the United States and Canada from a PC for free. To make a call with Google Voice, navigate to Google.com/voice/ and sign up for a phone number if necessary. Then click the Call button in the top left and enter the desired phone number to call.
When using Skype and Nimbuzz, both users must have the app in order for calls to be free.