Glassboard is a free app for sharing privately with different groups of people you know. You create a board – Glassboard term for a group – and invite people to it. These are the only people who will be able to see what’s posted to that board. The board members can share messages, comments, photos, videos, and even location.

Unlike most mobile apps, Glassboard is anti-social. Think of Facebook, but with private, focused groups. Each board is a silo, available only by invite. Boards are private from one another within the app. You can’t search for people you know like you would on Twitter or Facebook and neither search for groups.Only the people who are on your boards can see your information, which consists of your name, email and phone number if you care to include that in your profile.

The person who creates a board is the board chair. They can invite and remove members, change the board picture, and delete the board. The News Feed displays a collection of all the most recent activity from all of the boards that you belong to.

The app has been available for iPhone and Android since a while, and has just landed on Windows Phone. Glassboard has been developed by Sepia Labs, a product studio made up of former employees of NewsGator Technologies, including Brent Simmons (NetNewsWire, TapLynx) and Nick Bradbury (FeedDemon, TopStyle, HomeSite).