Google is actively rolling out a new feature, dubbed “People Widget”, that makes it easy to see more about your contacts and interact with them more effectively.
Next to all your emails you’ll see the widget which houses relevant information about the contact including things like recent email threads you’ve engaged in with them, shared calendar information, shared documents, Buzz posts, contact information (including quick access buttons for calling or chatting them), and more.
All of that information is currently available to you in some way but it’s spread out across services in such a way that it isn’t easy to immediately see the big picture and quickly utilize the information.
If you don’t already have the People Widget in your Gmail interface, expect it to appear some time in the next two weeks.
Introducing the People Widget [The Official Gmail Blog]