Google has just released in the U.S. a new version of Google Talk for the iPhone and iPod Touch browsers.   You can now talk with them while you're on the move in addition to sending your friends Gmail messages from your iPhone.

On your iPhone browser go to www.google.com/talk, log in and start talking. Google Talk runs entirely in the browser so there's no need to download or install anything.  There are a few differences from using Google Talk on your computer. For example, in to receive instant messages with Google Talk on your iPhone, the application needs to be open in your Safari browser. When you navigate away to another browser window or application, your status will be changed to "unavailable" and your Google Talk session will be restarted when you return.