You can use WhatsApp to send messages over WiFi or 3G to anyone else with the app installed on their phone. The software works across mobile operating systems (iPhone, Android, BlackBerry, and Nokia) so it will function with contacts who have other versions of WhatsApp installed.

Once set up, WhatsApp is pretty easy to use. Just type and hit Send to post the message. WhatsApp gives you a number of other handy options aside from just sending text. You can attach a picture (taken from your camera or stored on your device), audio, and video. There's also an option to email your chat history.

The Windows Phone version of WhatsApp is a bit more basic than it is on other mobile operating systems. For example, it doesn't save conversation histories and notifications don't work well.

Remember that WhatsApp only works if both people in the conversation have the app installed.

Overall though, WhatsApp makes for a handy way to chat for free on your Windows Phone device.

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Using Viber, you can connect with your friends from your contact list who already have the app installed. You can send them messages for free using the app, and receive push notifications that alert you when you've been sent a message from someone.

This beta version of Viber for Windows Phone has much less functionality than the iOS and Android versions of the app. The main feature that it lacks is voice calling - which is the signature function of the app on other mobile platforms. The developer does assure us that free voice calls will be added to the Windows Phone version of Viber soon.

Since this is a beta release of Viber, there are some things that don't work well in the app. It doesn't seem to sync with your phone's contacts list, for example. Also, it can take some time for messages to arrive on occasions.

Viber for Windows Phone looks great and is easy to use thanks to its familiar threaded conversation view. There are a few settings you can play around with, including toggling push notifications, location services and landscape mode.

It's also possible to attach photos to your Viber messages. Unlike WhatsApp though, you can't send video and audio, nor share your location or contacts.

Viber will be a lot more useful when free calling is added to it. For now, the limitations of this beta mean you're still better off using WhatsApp for free text messaging.

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The Nimbuzz app serves up an attractive user interface through which you can chat with any of your contacts on Windows Live Messenger, Google Talk, Yahoo! Messenger, or Facebook Messenger. Simple sign up with Nimbuzz and add your account details for each messaging service/social network and all your contacts will be imported.

To start chatting, simply tap on a contact and a chat window will open. Now you can exchange text messages for free and even send and receive photos with the other person. The options aren't quite as extensive as WhatsApp, which also allows you to share video, audio and location.

Other options within Nimbuzz include the ability to edit your profile and add status updates, track the history of your conversations, and add favorite contacts for quick access to your best buddies.

The Nimbuzz user interface is very attractive, allowing you to flick between conversations effortlessly, by swiping the screen. There are still some technical issues to be fixed in the app. For instance, we experienced problems with the import of Facebook contacts, testing on a Samsung Omnia W7. For some reason the names of offline Facebook contacts don't display properly.

There's no voice chat in Nimbuzz, but it does provide a simple and elegant way to chat with your contacts for free.

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The app is like a cross between Viber and WhatsApp. You can send messages with eBuddy XMS to anyone else who has the app installed, and vice versa.

To set up messaging with eBuddy XMS, you need to enter your phone number, and then an activation code (sent to you via SMS). You'll be issued with a PIN number once you've entered the activation code. You can then chat with anyone on eBuddy XMS, adding them as contacts by entering their phone number or PIN number. There's an option to scan your phone book or Facebook friends for any contacts who are using eBuddy XMS.

Disappointingly, unlike the iOS, Android and BlackBerry versions of eBuddy XMS, the Windows Phone version doesn't allow you to attach photos or videos, although it does allow you to receive multimedia messages from users who have sent you stuff. On a more positive note, eBuddy XMS for Windows Phone includes a group messaging feature.

In our tests on a Samsung Omnia W, eBuddy XMS crashed a few times, and hopefully these stability issues will be fixed in a future release.

Providing you can convince your friends to switch from Viber or WhatsApp, eBuddy XMS makes for a simple, free messaging app, although this Windows Phone version is quite limited.

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What does Hike do?

Hike allows you save the cost of sending SMS by exchanging free messages with anyone else who has the app installed, regardless of what smartphone platform they are using. Hike can even send SMS messages for free to someone, though this service only works in India at present.

Besides just chatting via instant messaging, you can attach images, video, audio and voice messages to your chats with Hike. There's also an option for sharing your location with the person you're chatting too. Hike includes a group chatting feature too.

Hike includes a wide selection of fun emoticons that you can add to your chats, which are grouped into three different types of character. There's something for everyone in there.

How easy is Hike to use?

The setup process for Hike is very similar to that of WhatsApp or Viber. You need to enter your phone number and you'll be sent an activation code via SMS. Enter this into the field provided and you're away.

You can easily view all your friends on Hike by tapping the contacts button. This will pull up a list of people from your phone contacts book who have Hike, as well as allowing you to invite friends who don't yet have the app.

Is Hike better than WhatsApp?

Ultimately, Hike is very similar to WhatsApp. It shares almost all of the same features, though I would say WhatsApp is a bit more polished. Although the user interface of Hike looks great, it doesn't have the customization options of WhatsApp, which allows you to change the background image of the chat window. WhatsApp has a more varied range of emoticons, too.

In our tests we had problems with the activation process, which the developer said was not working due to "high demand". Eventually we managed to register and test the app. In general it runs very well, but we experienced a couple of crashes, and had some problems sending attachments at times.

Hike is a fast and easy way to chat for free with your buddies on your phone. Whether you choose Hike over WhatsApp, LINE, Viber and the rest will depend ultimately on which service most of your friends are using.

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