Google integrated a Gmail Chat widget in iGoogle's sidebar. If you don't like the chat box, Google recommends to sign out of chat, although you could also change your status to "invisible". For those who want the old version of iGoogle: http://www.google.com/ig?gl=all.
In addition, orkut also added Gmail Chat. "To get you started, we've come up with a formula that automatically predicts which of your orkut friends you probably want to chat with, and only tells those people that you're signed into Google Talk. Our formula takes a bunch of things into consideration, giving preference to people who you've labeled as 'best friends' or written scraps to recently, and people who have friends in common with you."
In addition to showing Google Talk contacts, orkut will also add some friends you are likely to chat with. Like iGoogle's sidebar chat, orkut's chat boxes are persistent so you can visit different orkut pages while continuing to chat.
Source:→ Google System