A critical piece of human-computer interfaces is awareness, the ability of the human to know the state of a system. Most current software applications have a pretty linear model of attention: you're paying attention to the software like you're supposed to pay attention to the teacher in class. This is (in both cases) absurd: you've got plenty of other stuff on your mind. Because of this, awareness tends to be driven by interruption: think about the beep the indicates that you've got new email.
This is frustrating, though, because it's such a simple model, and it's so incredibly disruptive. As we start to use more and more collaborative systems, there will be a lot more for us to pay attention to. Actually, that's not quite the right thing to say: there will be more for us to be aware of. Awareness isn't really the same as attention, because my awareness of a process might take up only a tiny fraction of my attention. And my awareness might be quite intermittent.
There was an article in the New York Times a week ago about a new generation of devices that offered a non-interruptive awareness. I saw one of them at a Brookstone the other day. It's a globe that plugs into a phone line and changes color depending on how the stock market is doing. If the market's doing well, it glows green. If the market is down, it's red. (Of course the next generation ought to be tied to a specific portfolio.) This is great because the information, although quite unspecific and imprecise, is still filtering into your brain without causing interruption. It does this despite the fact that the information flow is effectively constant.
We need to develop a toolset of screen display interface widgets to convey awareness in a similar fashion. In fact, we need to think about a larger design space for awareness.