Chat with People in Mutual Circles (Google+)

More +ification of Google services

What's changed with Chat?

• Previously you could only chat with someone if you knew their email address. Now you just need to have each other in Circles.
• When you and your contacts have each other in Circles, you'll be able to chat with them across Google properties such as Gmail, Google Plus, iGoogle, Orkut, and the Google Talk Client.
• Instead of displaying all of your contacts in your Google Plus Chat list, we're displaying contacts from your most recent conversations who are online now. (You'll still be able to use the search box at the top of the Chat list to find contacts that aren't displayed.)

http://www.google.com/support/plus/bin/answer.py?answer=1709883