The spring update of the Live Dashboard, Microsoft’s online portal for the 360, is going to include an instant messaging function (basically Windows Live Messenger) with a keyboard accessory in the works.
As you can see from the image (click for a bigger view) the keyboard will plug into the headphone jack on the 360 controller. The only release date available from MS for the keyboard is “this summer”, until then an onscreen keyboard or USB keyboard will do the trick.
The messenger funciton in the dashboard will allow you to talk to up to 6 friends whether they’re using an Xbox, PC, or mobile phone. (From Joystiq.