If you are looking for a way to organize large local meetings, the Meetup app is a great way to go. Available for iOS, the mobile application lets you learn what's going on around you, do something nearby or share a gathering.
This works for a broad variety of hang-outs, from fitness to business and hiking to book clubs. It would also work for filming, language learning, parents, pets, photography, writing and a variety of other educational or social networking. Whether you are new in town and trying to meet like-minded people, or trying to organize an existing group, this app will be helpful.
The Meetup app helps you organize the events you want to go to, lets you send and receive messages, join groups and create a profile. The app is available for iPhone, iPad and iPod touches.