In reply to Philip:
We searched for months looking for a way for 5 of us to share a calendar.
Eventually, we set up a hotmail account for the business, e.g. Widgets@hotmail.co.uk.
Then in Outlook we each connected to it as a pop account. Disabled the email, (handled by another ISP, but also handled in Outlook).
We have a Livemail account to access directly to adjust settings etc.
Now this account allows us to share the one calendar, and a contacts list.
We can also have personal (Outlook Calendars), but these do not share, though each can view the personal and shared side by side.
Best solution we have had, and we tried and struggled with Exchange, and Business Contact Manager for years.
And its free.