The usual way is to have a webcam software that take screenshots from your office at regular intervals (5 seconds, for example). Those screenshots are automatically uploaded to a server (or the server is run within the software itself).
Then you create a webpage which gets the JPG and refresh automatically each 5 seconds. Every user who visits the page will see autorefreshing the image, so it seems a real time flow.
Thats the basic way. A more sophisticated method is using a service like Ustream or Mogulus which allows you to create a real time video flow.