Meetup.com

General Information
Cost: 
$12/mo for Group Organizers only
Description: 

* Meetup is the world's largest network of local groups. Meetup makes it easy for anyone to organize a local group or find one of the thousands already meeting up face-to-face. Easy group management so that you don't have to make an entire website from scratch.

* Each organization can list themslves on a page, including a logo, description, useful links and who are founders and who are attending the next event. They can also alert members of their upcoming events. Users can join groups to get updates of when each group is holding an event and see who else is attending events they sign up for.