WhatsApp just released a Public Beta of their application, for the Symbian OS.

(Just so you know, this is a screenshot of their iPhone client)
WhatsApp is a cool little application that allows you to chat with other users of the app, and not have to pay SMS text rates as it’s all via the Internets! The app has been out on iPhone and Blackberry OS for a while now.
“WhatsApp Messenger is a smartphone messaging app which allows you to exchange messages with your friends and contacts without having to pay for SMS. WhatsApp Messenger is cross platform and is currently available for iPhone and BlackBerry and yes, iPhones and BlackBerries can message each other too! To send and receive messages, WhatsApp utilizes your existing smartphone internet data plan: 3G/EDGE (or Wi-Fi when available)
In addition to messaging, both iPhone and BlackBerry WhatsApp Messenger users can send each other unlimited images, video and audio media messages.”
Sounds interesting enough to try it out? Head on over to their site to download and try it.