You can share a calendar and assign permisssions to the calendar. The users
has to access the calendar using a URL, for example:
http://virtual_server_name/exchange/username/calendar (KB821900)
I don't think is possible to add an appointment without using third party
applications.
/Daniel
> Is it possible to create a shared corporate calendar and enable users to
> indicate they are participating in the event.
>
> Is it possible for them to add an appointment from a shared calendar to
> their personal calendar?