We want to find an easy way to track how many people from our invitee list actually signed up for or donated to our event. I was planning on putting all invitees into a 'group', and then tracking RSVP's in CiviEvents. We do physical mailings instead of e-mails right now, so if we can trim the list of people we know don't attend or donate it could save us on postage. Would anyone know of a way to pull a report on this somehow?
You could create custom Event participant Status called Invited. In the settings set the Class to Waiting and leave the Counted checkbox unchecked. When you mail out the invitations register all the people to the Event with the status of Invited. As you receive the confirmations go in and set each to attended. Then you can do Event reports based on who has attended or not.