1. Fring
Fring has a lot going for it, from calls to chat to video calling. This app lets you add other communication services from AOL to Google Talk as well as connecting with your phone book, letting you talk with anyone on just one app.Of course, the catch for free calls is that the other party needs to have Fring on their phone, which isn’t a problem since it is available not only for Android, but also on iOS, Nokia and via a mobile browser. Their newest feature is being able to video call with up to four people at a time over any data connection. It’s fun to try out but a bit choppy.
You can also call to regular phones by buying some credits so you can talk to landlines and feature phones locally and abroad.
2. Nimbuzz
Nimbuzz is like a swiss army knife for calls and messages. Bring over friends from Facebook, ICQ and yes, even MySpace. You can make free calls once they’re on Nimbuzz, as well as free texts and free video, photo and music sharing. It works on almost every phone out there from Android to iPhone, from BlackBerry to feature phones that can run Java apps. It’s also available on the desktop so you can call people over your laptop or on your Mac.While it might not have any fancy video calls, you can still use it to make regular calls using credits and it also has a webchat feature if you want to connect with friends using other computers (like when at an internet cafe).
3. Qik
If the spotlight of video beckons to you, Qik delivers. Not only can you make one-on-one calls, you can also broadcast videos live as well as drop in on video feeds of your friends. This app, of course, needs the other party to have Qik installed, which is available on Android and iOS and other phones. You can also share videos to a myriad or other services like YouTube, Facebook and more. Just remember that for calls, this works best with a front-facing camera.
4. Skype
Any free calling list is never complete without the ever-ubiquitous Skype. It actually has verb status, with Skyping becoming synonymous to calling over a computer. While it did start its service using computers, mobile has benefited greatly by the many apps the company has released. You can call almost any computer and any phone for free provided they have Skype, and most do since this is almost a requirement for any device.If you want to call regular phones, Skype also has you covered and all you need is to buy credits (a bit pricey though compared to Fring). The Android app allows you to add your contacts so you can call them through Skype or send them IMs. In select Android phones, you can even make video calls.
5. Tango
This was the go to video call app for many who were snubbed by Skype not letting calls over 3G. Tango lets you make voice or video calls using your Android phone using any data connection you might have. It takes the best video calls around, being good enough to be featured on TV several times. And yes, it’s free if both you have Tango (since it does take two for it to work, as the saying goes).
6. Tru App (formerly Truphone)
The difference between this and other calling services is that Tru offers its own SIM card. That means you can buy a SIM and don’t need to worry about high roaming charges or finding free hotspots, and you also get to keep your existing number. If you don’t want to shell out for that, the Android app is free and you can call other Tru users, even those on Skype and Gtalk.
7. Viber
Ported over from iOS, this is one of the most straightforward free call apps out there. Install it and it scans your address book, connecting you with other Viber users without the need for silly usernames and email verifications. Your user ID is your phone number.You can go ahead and put it in your home screen since you not only can make free calls to other Viber users, you can also send messages to them, make regular SMS and calls and even email right from Viber. The one thing Viber is proud of is its call quality: very clear audio with no lags, as if you were using your regular line. This is one app you need on your Android.
8. Yahoo Messenger (needs this plugin for calls)
Yahoo might not be big in other parts, but it’s still big in Asia. Their messenger app is the IM avenue of choice for many in this part of the globe and the Android app is no different. If you have Froyo on your phone, you can initiate calls (make sure you install the plugin above) and even video calls from their app. On top of that, Yahoo can send free international SMS, chat with FB friends and more.
9. ooVoo
An
eagle-eyed commenter pointed out this app. It sets itself apart by
giving you 6-way video calling over 3G or 4G (not free) and group video
chatting (free). ooVoo,
like other apps, is free and hands out free calls to other users. It
only has a shortlist of supported phones though but I think they’re
working on expanding that. And if you have a website or blog, you can
put a link there so people without ooVoo installed can still call you
over the web.Source: http://www.androidauthority.com/top-best-free-calls-android-phones-voip-19829/