Yammer, an enterprise microblogging platform mirrored after Twitter, launched at TechCrunch50 this year and grabbed the attention of everyone.

Yammer was developed by a genealogy site called Geni that was looking for a way to improve internal communications. David Sacks, founder of Geni, liked the finished concept so much he decided it would be worthwhile to spin off as its own company, offering it to other enterprises as well.

The purpose is to allow co-workers to share status updates. You post updates on what you are working on. You can post news, links, ask questions, and get answers for people in your company.

You can see most the most prolific people and the most followed people. It is a good way to discover who is the most influential in your company.

To start using Yammer in your company is very easy. Anyone with a company email address can start the Yammer network and begin inviting coworkers. Each network remains private by limiting access to those with a valid company email address. Yammer also states that information is never shared with third parties.

The basic service is free, but Yammer’s business model is built around taking ownership of the network. Companies can pay a monthly fee to claim and administer their networks, giving them the ability to delete messages or users, set password policies or identify specific IP ranges for who has access.

To keep Yammer competitive with comparable public platforms, they’ve also got an Adobe AIR desktop app, an iPhone app and a Blackberry app, which should satisfy three of the biggest user groups in the corporate environment.