Inviting guests to your event on Twitter

A really great app to promote events online is Twtvite.com A great functional app that allows you to enter your event and post to Twitter and groups

A great feature is that Twtvite allows users to RSVP to the event by entering their Twitter profile, thy can also RT the event, or you can post it on Facebook or share it on other social networks.

See below for a screenshot of an event invite. As an organizer of an event you enter necessary who, what, where, info, then when users visit the page they see all the information on the event and can even leave comments.
Taking it to another level Twtvite will also show a google map showing exactly where the event is taking place.