Zoji - As claimed by the developers of this Zoji, it caters online tools to aid you plan activities off-line.

EventTitans - Top rated event management software

Evite - Send online invitations for all occasions by email or text message. Create invites for birthdays, baby showers, save the dates, or customize your own design.

Tix - Tix is a state-of-the-art, cloud-based ticketing system that features fully integrated access controls, event management controls, multi-channel distribution capabilities, and a robust reporting suite.

PurpleTrail - Whether it is about birthday or wedding party or holidays, you just need to name the event and PurpleTrail will provide you the apt invitation solutions.

Brushfire - Brushfire offers tools for online registration and event management.