The Network Event Calendar plugin by aut0poietic is a very simple Event Listing and Management WordPress plugin. What makes this plugin different from the multitude of other plugins that do the same job is that this plugin is WordPress 3.0.1 Multi-Site Network Aware.
For the theme developer, the plugin exposes API methods that mimic the behavior of standard WordPress methods; the_events, get_the_events and get_total_events. Full API documentation exists.
Download and Info: http://wordpress.org/extend/plugins/network-event-calendar/