Event-O-Matic is a plugin by mjgarvi that allows quick and easy display of event listings on your website. Unlike other event plugins, Event-O-Matic allows your web audience to submit their own events and gives you the ability to moderate these events as they arrive to your site. Edit or reject submitted events and add them to your listings for the ultimate social driven event service. Event-O-Matic is also fully integrated with Google Maps to give each event a clear location service.
Download and info: http://wordpress.org/extend/plugins/event-o-matic/