Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Punchbowl - A party planning and greeting card website
Invitime - Meet new friends and challenge them to invite you
RSVPify - A powerful and awesomely customizable platform for selling tickets online for your event.
RSVP Keeper - Online RSVP's made easy
Online-RSVP.com - Beautiful online RSVP for wedding & other events. Create an online invitation, track your guests responses.