From the Official Google Blog:
We’ve been working with AOL on ways to let our users talk to their buddies on the AIM network, and I’m delighted to announce that the fruits of that labor are live. Starting today, Gmail users can sign into their AIM accounts via Gmail chat and talk with AIM buddies just as they do with their Google Talk friends. Best of all, the features you love most about Gmail chat, such as chat history and automatic sorting of your buddies based on frequency of communication, work seamlessly across your Google and AIM buddies.
I love to see common standards and different services working together. Let’s hope we see more collaboration like this!