Invite Up is one of the simplest online Invite tools that I’ve ever seen. It’s a micro site that you can use to view responses from people that you’ve invited online. No signing up, no email required. All it will ask from the people that you’ve sent the invite with are their name/nickname and response (yes, no, maybe).
To use the application, all you need to do is generate a fresh invite link that you will send to your friends. A special URL/link will also be generated only for you. You will then use that special link to check out the responses to your invitation. You’ll see the names and their responses on that link.
Invite Up may be simple but it works. This is great for casual invitations where you can mass email your contacts and anyone can just reply a maybe. Great for parties and non-formal gatherings where anyone can just come as they please.