Microblogging platforms are very popular since the rise of Twitter.
People who own platform to develop with the same functionality as Twitter can do that with the open source software StatusNet.
UPDATE: StatusNet is unfortunately no longer active since 2015.
StatusNet was formerly known under the name of Laconica. SatusNet offers the same functionality as Twitter, but is open source. Everyone can this so free to use your own server space a microblogging platform to install. Users can then post messages to that internet domain.
In addition to the software download you have to install, there is also a hosted version available. The domain of the microblogging platform looks then like this: uwdomein.status.net. The hosted version of StatusNet is also free to use, you don't need a own server space to buy or rent.
A working installation of StatusNet was formerly to see and try on Identi.ca. We are currently running the network on a different platform.
StatusNet has the following characteristics:
You can free download StatusNet and safe install the latest trial or new full version for Windows 10 (x32, 64 bit) from the official site.