What is a Twitter alternative for internal teams?
My answer to What is a Twitter alternative for internal teams? on Quora
Yammer is the most obvious tool here.
Campfire are other chat apps fall into this category.
I once wrote a Twitter clone for a team of people working on a project in a Napoleonic Sea Fort with no Internet connection—it’s a very simple system but it’s a lot of fun. You can get the source code for it on GitHub: http://github.com/simonw/bugle_p...