The node_invite module is similar to the RSVP module that already exists. In fact you probably want to check that one out too.
Goals of this module:
- Invite anonymous users to any node
- Manage invites
- Users receive an email with a unique URL in it so that they can answer your invite (Accept, Deny, "Maybe")
- Users can add comments (if you enable that feature) to any invite response (useful for the "Maybe" people)
- Tokenized email notifications
- Tokenized forms (RSVP accept/deny)
- Configurable notifications (who gets notified about what)
- Very nice invite manager (re-send, revoke invites)
- The module creates entries in $node->links
- A video tour is available online.