AltaBird.com

Events can be setup on the network and members can choose to attend them. Like groups, each event has it's own profile. Event attendees can add photos to an event, invite friends to join, participate in discussions and send bulletins to other attendees.

You can browse existing events under the tabs here or create your own. Next to each event you can see the list of actions you can perform. If an event is private, you will need to request membership to be able to join it.