BlackBerry Messenger combines the reliability and exceptional user experience of BlackBerry with the familiar look-and-feel of instant messaging programs that most people are already used to.
It's designed to allow you to have a PIN-to-PIN messaging conversation with another BlackBerry user.
It also supports group chat, File Transfers, Checking your message delivery status and your Contact status. You can also search for PIN, by searching the PIN stacks, adding the PINs of members of Pinstack.com
It is totally free
To download Blackberry Messenger, click here
You can also download directly to your BlackBerry, to download directly to your blackberry point your Blackberry browser to: