Evite

 Evite  is an event hosting silo launched in 1998 that uses email for inviting and signing people into events, and there are no known IndieWeb Examples of folks POSSEing event posts to Evite.

Features
Evite allows you to
 * create/edit/delete event posts
 * invite people by email, optionally allowing them to note a +1 (plus one) or more up to a limit per person
 * RSVP using a special link you received in email
 * note a +1 (plus one) or more than one up to the limit allowed by the event

POSSE
There are no known IndieWeb Examples of people POSSEing their event posts to Evite, though it would be possible to do so.