A user asked:
Is it possible for me to invite other people to a meeting that was sent to me? I'm an invitee, not the organizer.
Yes, you can but you should follow good meeting etiquette when inviting others. This means you ask the organizer for permission to invite the other people. Ideally, the organizer will invite them, but reality is that many organizers will allow you to invite them yourself.
To so this, select the meeting and forward it to the others. Exchange 2007 and Exchange 2010 will send a message to the organizer that the meeting was forwarded.
When the newly invited accept (or decline) the meeting, the organizer will receive the notification and their name is added to the optional attendees.