For a company events calendar, you can simply create a new Calendar folder in Public Folders and grant permissions through the Properties dialog for the folder.
Outlook 2007 adds the ability to send calendar files and publish your calendar for sharing. This supports just one way sync - the sender can update the calendar but others can't. If all users need the capability to update the calendar, you'll need to use one of the tools below.
More Information
For additional information on group calendaring, see Maintaining a Group Calendar in Outlook