Android (search results)

textPlus
Cost: NOT Free

textPlus is an app for sending chat messages and traditional sms. Compatible with the iPhone, iPad, iPod Touch and now Android and any SMS enabled mobile. Message for free between textPlus users anywhere in the world and if you're in the US you can send sms also.

Has push notification so that you'll never miss a message, and you can easily send group messages.

WhatsApp
Cost: NOT Free

WhatsApp is a mobile messaging app that works on several platforms. It allows you to send free chat message from your mobile phone to other mobiles which also have the WhatsApp application installed. The app costs €0.99 to download.

Currently works on the iPhone, Blackberry, Android and Nokia platforms. It does NOT work on the iPod Touch or iPad. WhatsApp for Android 2.x and Nokia Symbian S60 is in beta.

As well as chat messages, you can also send images, video and audio messages. WhatsApp confirms that messages have been delivered by marking them with a little green tick. This app comes in several languages too, including English, Dutch, Finnish, French, German, Italian, Korean, Russian, Spanish, Swedish and Chinese.

Skype
Cost: FREE

If you already have a Skype account downloading their mobile app will not only give you free calls to other Skype users from your mobile and cheap mobile calls to landlines, but it will also give you free messaging and group messaging to all your Skype contacts. The app is free to download and works on the iPhone, iPod Touch, iPad, Android and Symbian (Nokia). If you live in Australia, Ireland or the UK and have a 3 network, you can use Skype too (even on your BlackBerry).

Nimbuzz
Cost: FREE

Nimbuzz is one of the most popular mobile messaging apps because it works on all platforms. You get free messaging (and phone calls) to any other Nimbuzz user wherever they are in the world.

Better still, by adding your social networking logins, such as Facebook, to your Nimbuzz account you can chat for free to all your social networking friends and contacts directly from Nimbuzz too.

eBuddy
Cost: FREE

eBuddy is a mobile messaging app and a web messaging service. With eBuddy you can message to MSN, Yahoo, Gtalk, Facebook, ICQ, MySpace and AIM (AOL).

There is a specific eBuddy mobile app made for the iPhone and for Android (the Blackberry app is coming soon); however, the eBuddy Mobile Messenger is compatible with many mobile phone brands (check the eBuddy website to see if your particular model is compatible).

As well as sending free chat messengers between eBuddy users and your social networking friends, you can send photos directly from you phone camera, give yourself an avatar, and even send chat messengers to users who are offline - they will get your message as soon as they sign in again.