Punchbowl - A party planning and greeting card website
Attendize Event Ticketing - Attendize is a free & open-source ticket selling and event management platform
RSVPify - A powerful and awesomely customizable platform for selling tickets online for your event.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Online-RSVP.com - Beautiful online RSVP for wedding & other events. Create an online invitation, track your guests responses.
pretix - pretix helps you to sell tickets for your event in an easy way. It supports multi-lingual events and provides a wide range of features