Lets look at some of that popular instant messaging apps available for your Windows Phone:
System Integrated: Facebook and Windows Live Messenger (msn)
Facebook chat and Windows Live Messenger are built in and deeply integrated into the system. This means that you don't require any third party apps. All you need to do is go to your messages and start a threaded conversation with anyone. You can switch to Text, Facebook or Windows Live chat at any time. The entire conversation stays in one thread irrespective on which medium you are chatting with the person to.
IM+: Beep, Facebook, Yahoo, Google Talk, Skype, AOl, ICQ, @Mail.ru, Yandex IM, MySpace and Jabber
IM+ is a great multi platform messenger app. It lets you connect the above mentioned accounts. It supports live tile and toast notifications and with Mango it also supports staying connected in the background. I would recommend IM+ for any other accounts except Facebook, as Facebook is already deeply integrated into the operating system. IM+ is also only viable app to use for Skype (text messaging, no voice or video calls).
The app supports a wide variety of settings like showing online contacts only, showing groups, notifications for new messages received or when a contacts goes online, push settings, font size and so on. The in-chat conversations also support receiving and sending of images directly from the camera or gallery as an attachment. The Push-to-Email option allows incoming messages to be forwarded to your email. This is useful when the IM+ app is not running or when the wireless connection is lost. Also when in push mode, you can set to auto reply a custom message.
These features make the IM+ a great app for getting connected to other cross messaging platforms.
WhatsApp: Cross platform smartphone messenger to get connected with other WhatsApp users. No need to create an account. Account is associated with your mobile number.
WhatsApp became quite popular over other platforms like Android, iOS and Symbian. The Windows Phone app helps you get connected to your contacts who are on WhatsApp across any platform. Immediately after installation, the app scans your contact list and lets you know who of your friends are on WhatsApp. This app is recommended for getting connected to your local contacts if you want to communicate with them without sms-ing. Another good thing about this messenger app is that it stores the history of the conversation. The app also supports push notifications and Live Tiles. Along with sending photo attachments you can also send an audio note and share your location with a contact. The app shows if the message has been sent, delivered or even read.
Kik Messenger: Independent Cross platform smartphone messenger to get connected with other Kik Messenger users. You need to create a Kik Messenger Account.
Kik messenger is a real time mobile messaging app and is developed by Kik Interactive. Kik messenger is available for the iPhone, Android and now Windows Phone 7. You can chat with your friends across any platform. There are over 4 million people who use Kik. Even if your friends are not on Kik, you can invite them to join up and create an account on Kik and start chatting in real time.
This messenger is completely free and features group chat, picture sharing, live tile support, offline messaging support, push notifications and detailed message status.
You can also check out our in dept review of Kik Messenger.
If you use any other instant messenger apps for Windows Phone, we would love to hear your experience with it in the comments.