An ability to have informal video chat with my colleagues who may be in the building as I am, working from home in same city or are offshore. But video chat never caught mainstream for all the good reasons.
I started pondering on the creating solution myself: www.remoteoffice.me. And right then Google announced WebRTC. It was a happy co-incidence and I thought this would do it.
Now that Google+ APIs are in the pipeline I am looking forward to build an app that would allow meeting rooms, white-boarding, taking/assigning actions items, sending status updates, knocking on the "door" to see if you are available for a minute ...
EDIT: Chris Brogan on 50 things that are with Google+