Glassboard is a social networking app with the emphasis on privacy. You share messages, photos, and videos only with the folks who you invite to participate. It's designed for small work groups, class projects, friends, any group that wants to have a private way to keep in touch on a topic. Facebook is fine for those family reunions that you want to share with the world, but there are times when you want to keep things private.
Once you open a Glassboard account, you can create as many boards as you need, and invite people to join a board via email. Once people join, they can post comments, and see the comments that others add. Glassboard has push notification, so you're updated whenever someone adds information to your board. You can set "quiet hours" when you don't want to be interrupted by traffic on a board.
There are Glassboard apps for iOS, Android and Windows 7 phone devices. You also can sign in and participate with your group via a web browser interface.
Glassboard is free. Check it out here http://www.glassboard.com/
(I have no connection with Glassboard, just thought it looked useful.)