It looks like Google will be integrating Gtalk, their IM client, into Gmail in the next few days. I found this on the main gmail login page.
Chat with your friends from right inside Gmail. There’s no need to load a separate program or look up new addresses. It’s just one click to chat with the people you already email, as well as anyone on the Google Talk network. And now you can even save and search for chats in your Gmail account. "
