The call quality is clear, as if you are using a phone to make the call. You can even add contacts to your Vox.io account manually, via a contact file saved in your PC or through Google Contacts. If you like the service, you can even invite your friends to try out this useful application. The service is still in beta stages so you might experience difficulties while calling.

It’s free to call other Vox.io users but if you want to make any international calls, you must buy Vox.io credit. You can check out Vox.io call rates here.

Features

• Simple and easy to use.
• Call friends through browser.
• Upload contacts from your PC.
• Free calls with other Vox.io users.
• Buy credit and make cheap calls.
• Free calls to other Vox.io users.
• Link Google, Twitter or Facebook account with Vox.

Check out Vox.io @ http://vox.io

Twilio Client is a free to use web app that lets you call numbers in the US. All you have to do is type in the recipient’s phone number and click on the Call button. The Hangup button can be clicked to end the conversation.

In case you need an excuse to end the conversation quicker you can add special environment sound effects. Buttons for these can be found at the bottom and correspond to sounds at the airport, a baby crying, or being in the toilet.

Features:

• A user-friendly web app.
• Lets you call phone numbers in the US.
• Provides sound effects for different environments.
• Effects help end the conversation quicker.

Check out Twilio Client @ http://www.twilio.com/api/client (By Umar from AllThatIsApple)

The service is only available in the US since it has local access numbers only for the cities in the US. The calls will last for 10 minutes, and if you are calling the same number twice or more, the call is cut to 5 minutes to avoid phone spam.

Features

• Make free international calls from the US.
• Need to listen to audio ads.
• 10 min call limit.
• Dial the local access number for your city to connect.
• Similar tools: CallingAmerica and more in MakeUseOf’s free calling category.

Check out FreePhone2Phone @ www.freephone2phone.com (by Abhijeet from Guiding Tech)

As you can see in the above screenshots, the tool has a neat user interface. I didn’t get a chance to try it, but if it works, it’d be a pretty good deal for iPhone users, provided their service provider doesn’t charge exorbitant 3G rates.

Features

• iPhone app to make free calls
• Calls can be made over 3G or Wi-Fi
• No other charges except for data charges
• Call anyone with a phone number (and who has Viber) for free

Check out Viber @ www.viber.com (By Abhijeet from Guiding Tech)

When anybody click on that unique link, they’ll be able to call you without actually seeing your number. You can receive the callas on the number you specified or your Skype. You can send the tweet out for all your followers or address it to specific users. You get 30 minutes of call forwarding for free. You can also set the link to expire after a specific duration such as an hour or 2 hours.

Features:

• Let your Twitter followers call you.
• Calls are forwarded to your mobile phone or Skype.
• Your number is never displayed to anybody.
• Set your link to expire after desired duration.
• No registration required.

Visit Zin.to @ www.zin.to

All your users need is a microphone to talk to you. Zingaya also gives you a virtual private number that can be forwarded to any phone line. The Zingaya widget can be integrated on any website for customer support, e-commerce, social web or any other purpose. It lets you receive calls on one line for free, additional lines can be obtained for a small monthly fee.

Features:

• Allow your visitors to call you from your website.
• Receive the call on land line, mobile or Skype number.
• Record web calls and store online.
• Receive unlimited number of calls.
• Get additional lines and widgets for a small monthly fee.

Visit Zingaya @ www.zingaya.com

Suppose you are living in New York and you place a call to Moscow, while paying the New York to New York call rates. This is exactly what Rebtel does.

Rebtel is a cellphone app for Android phones. When you place an international call through your cellphone, Rebtel intervenes and finds a local number which can route your call. The only condition is that the number you call must also be on an Android phone that has Rebtel installed. The app works on your regular phone carrier’s service ““ no internet connections are required.

Features:

• Free Android to Android international calling
• Very simple to use.
• Uses advanced call routing to place international calls through local phone numbers.
• Lets you make international phone calls on local call rates.
• Works only for Android phone owners placing calls to Android phones.
• You do not need to launch the app ““ it works automatically.
• Similar tools: Fring, dukaDIAL, All Free Calls, Talkster, EvaPhone, CallingAmerica, Foonz, FlashPhone, ViaTalkFree and TruPhone.
• Also read related articles:
  The Best Sites For Making International Calls
  6 must-know Apps to make FREE Group Conference Calls

Check out Rebtel @ www.rebtel.com/en/Services/android or search for the app at the Android Marketplace. (via LifeHacker)

After signing up for a free account, you can start adding contacts to start and receive web calls. The contact list manager allows you to add friends for quick calls and IMs. Moreover, this slick tool lets you save and view your call history.

Flaphone uses Session Initiation Protocol (SIP) to call other Flaphone users, SIP phones, and any phone numbers using SIP provider accounts. Additionally, you can install Flaphone to your desktop with Adobe AIR. A version for Google Chrome OS will also be available in the future.

Features:

• Free browser based softphone that allows you to contact other Flaphoneâ„¢ users, SIP phones, and landline and mobile numbers using an SIP provider.
• Processes incoming calls.
• No NAT and firewall problems.
• View your call history.
• Can be installed as a desktop application.
• Allows video calls and instant messaging with other users.
• CallMe widget that can be embedded on websites.
• Similar tools: FlashPhone.

Check out Flaphone @ www.flaphone.com

The service, as they claim, is supported by a reliable system specially developed for providing users a consistent and efficient communication service.

Features:

• Receive calls on Skype from the landline phone for free.
• Sign up, get an online phone number and a private extension and answer calls from your Skype.
• Provides numbers in more than 40 countries.
• Supported by a reliable communication system.

Check out Ring2Skype @ www.ring2skype.com (by Abhijeet from Jeet Blog)

• International dialing codes lookup.
• Simple and clutter free interface.
• Similar website: Tp2Location.

Check out SimpleCountryCodes @ www.simplecountrycodes.com (via Redferret)