NOTE: This suggestion is for Confluence Server. Using Confluence Cloud? See the corresponding suggestion.
We see that this plugin is available only for Confluence 3.4 until 4.1. It would be great if we could have it in the latest version of Confluence.
Event Calendar: Meeting Invites, Attendees/Confirmations, RSVP, Max Spots and Public Regiration
Make RSVP Plugin available for Confluence 5 onwards.