Many of us have a distributed work force which often leaves people wondering what others are doing. Twitter is a great service for updating status. Unfortunately twitter if often down these days. Also there is a privacy concern. Ideally you would like to host such a service yourself and also be able to restrict access to the site to ensure privacy.
Prologue, a twitter like WordPress theme, offers a simple way to update status of each other. We have started using prologue at corp.taragana.com. It is a password protected site, protected using modified version (ask me if you are interested) of WordPress Authentication plugin. This allows our workforce to communicate with each other as well as see what others are doing.
For a moderate to big company communication is always a problem. However writing blogs is often not an option for executives on the move. A twitter like service can easily change the landscape and provide for a much transparent organization.