Having a free SIP
account is a great way of making free calls on the Internet. You only need to choose a SIP provider that gives you a SIP account for free. There are many of these. Here is my list:
koenkooi/Flikr/CC BY 2.0
GetOnSip is a straight service offered by Junction Networks, the company behind OnSip.com, offering free SIP accounts in a very simple and easy registration. The registration fields stand right in your face as soon as you load the home page. You are not restricted on the amount of SIP accounts, and you get free SIP voice and video calling service and XMPP messaging. GetOnSIP also offers paid business SIP accounts.
IPTel provides IP telecommunications services and hosts several projects like the SIP Express Router, SIP Express Media Server and the SIP Express Router Web. They also provide on their site a wealth of information on Sip communication. The free SIP account they offer is of good quality and is also straightforward to register.
Ekiga is a VoIP service that offers a softphone and free VoIP service, and it is known for its Linux VoIP app. Ekiga also offers free SIP addresses that you can use with any SIP-supporting softphone app.
Sip2Sip is a rather straightforward SIP service, offer by ag-projects.com. It is a free SIP service based on fair use policy and no support. Registration and account management are easy. AG Projects has lots of products and offers this free SIP service for users to test the features present in its products.
AntiSIP offers a set of SIP-based services among which is the free SIP account, to which you can even receive landline calls, for example through the free US numbers provided by IPKCALL.
VoIPUser SIP account is a community effort of VoIP
enthusiasts. Do not expect much support from them. The registration process, while being straightforward, is rather restrictive. But if you believe in community efforts, check them out.