Competition among VoIP companies has become so fierce that they are not only offering free VoIP services but also permitting you to select an area code different from the area in which you live. This allows you to get rid of long distance charges if you call a number in your area code regardless of geography. Some companies are putting forth plans that include flat rates for international calls, which can be purchased by the minute at a discount to traditional phone carrier rates. Conspicuous features offered by the prominent VoIP services are as follow:

Yahoo: Yahoo has recently designed Yahoo Messenger with the ability to make free VoIP voice phone calls. Both the communicator should have this program. By clicking call-button at the top of your Yahoo Messenger chat box, you will be able to use free VoIP technology to send a phone call to your friend's computer. Another advantage to Instant Messengers is that it allows free VoIP calls to more than one person. Thus, this program has unlimited potential and can be used by distant employees for a conference call. Moreover, customers are able to customize ring tones, just as they do on their mobile phones. New beta versions of Yahoo Messenger service will includes improved photo sharing and spam protection tools and allow users to leave voicemail messages.
CosmoCom: CosmoCom's eye-catching feature is universal access contact center system it is a unified contact center suite that includes Automatic Call Distributor (ACD), interactive voice response ( IVR), Computer telephony integration CTI, multimedia recording and administrative tools. It is a high capacity, high availability, multi-tenant platform that supports multi-channel contacts including telephone, email, voice mail, and web chat/voice/video/collaboration.

Skype: skype is among those companies that offers free VoIP experience. Skype let you to make a PC-to-PC call to another Skype user. Skype allows you to download its free software. Then you can make call to the other user with same software. Skype has skypeout facility to call on other peoples' phone and skypein facility allows you to receive phone call from them. Skype Voicemail takes your calls when you are busy or offline; Skype SMS lets you send SMS messages to your friends' mobile phones from Skype.
iConnectHere Broadband Phone: iConnectHere offers lowest calling rates for r local, long distance and international telephone calls. It offers great savings on internet phone services such as Broadband Phone, PC to Phone and Virtual Calling Cards to businesses and consumers worldwide. Make phone calls from your PC at rates as low as 1.1'/min and per-minute or monthly plans. It is offering unlimited calling to USA & Canada and its plans start as low as $15.99.
AdCalls: AdCalls give you the opportunity to make calls to anyone in the USA and Canada at anytime on their home, business and cell phone free of charge. You can call on to anyone on his personal computer if both of you have AdCalls software downloaded.