In Microsoft Outlook, making someone an 'Optional' attendee is the same as Cc'ing that person. Making someone an 'Resource' attendee is the same as Bcc'ing that person.

So, to Cc someone to a meeting:

1. From the open meeting request, select the Meeting Planner (Outlook 97), Attendee Availability  tab (Outlook 98/2000), Scheduling tab (Outlook 2002/2003), or Scheduling Assistant (Outlook 2007)
2. Select Show attendee status.
3. Click in the Attendance column, and change the attendance for the person to Optional Attendee .

You can also click the To button on the Appointment page and put the person in the Optional (or Resource) list.

Another method for BCC'ing invitees is to forward the meeting as an iCal. Add the attendees to the message BCC field.

Great tip and a question I'm frequently asked when providing Outlook support.