Free Although it's not the best communication app for Android, Skype is definitely useful for keeping in touch with certain people like long-distance relatives or friends. Users can place free voice and video calls and also send instant messages to other Skype users on almost any device. When placing a video call, you can switch between your front and rear facing camera. Now with a revamped interface, Skype has a whole new look and a few new features, such as sending video messages to offline users.
FreeGoogle Voice offers low-cost international voice calls and unlimited free text messages for your unique Google Voice number. The app also includes group messaging, offline voicemail, and conference calling. Users have the option to read transcripts of their voicemail (though this depends on the quality of the call, making it a far from perfect feature) and record their incoming calls. One thing to keep in mind is that when placing domestic or international calls, Google Voice for Android will use minutes from your cell phone plan, so watch out.
FreeAre you paranoid about your texts being seen or accessed by someone other than the recipient? If you are, then this is the app for you. TextSecure has you create a password upon startup and then proceeds to enter your existing SMS and MMS messages into an encrypted database. You can also send secure texts from the built-in messenger app or participate in a group chat. One downside is that the text is only encrypted when the recipient is also using TextSecure. On the up side, the settings on this app are pretty powerful, giving the user a range of options. The app itself isn't perfect, but it is certainly a viable option for someone who is looking for a decent secure texting app.
FreeOf all the texting applications available, WhatsApp probably has the largest user base. It supports Android, iOS, Symbian, Blackberry, and Windows Phone smartphones. Feature-wise, it has a few more customization options than your standard text-messaging service: multimedia messages, inserting emoticons, and changing the conversation's wallpaper are among its abilities. Another awesome feature is the group messaging with titles you can edit. What makes WhatsApp better than regular texting is the ability to leave the conversation to avoid pesky notifications after you've had your say. Unless you're satisfied with your existing instant messaging app, then you'll definitely want to try this one out.
Free This VoIP app aims to improve users' talk and text experience with some impressive features like OS integration, group chatting with up to 40 people, no ads, and push notifications even when the app is off. You can save money in the process when you send free calls and text messages to other people who use Viber (though it only applies when you're on a WiFi network). Users also have the ability to transfer their conversation (voice or text) to their desktop provided they have the Viber software installed. The app itself is well-designed and if you're looking to save money in voice calls (especially to other countries), Viber might be what you're looking for.
Source pcmag.com
Top 5: Free Android Texting Apps