Well, this is exactly what Yammer provides as is an instant way to tell your colleagues "what am I working on?"
Yammer (www.yammer.com) addresses the issue of using your Twitter status for updates that are really only relevant to others in your company and offers a restricted area (and therefore hopefully a more open conversation).
Also, in a very Twitter-esque way, you can add hashtags (themes or subjects preceeded by the # symbol that you want to subsequently track, e.g. #takeover)
Here was their intial introduction at Techcrunch last year:
So, to answer the question "Is it any good?", my answer is a resounding "Yes". We at Ideal Interface have now been using it for a few weeks and are finding it a very useful way to share: thoughts, status updates, useful links and other info. It particularly suits our business as we are mainly out of the office (myslef on client sites most of the time and others working from their home offices, etc.)
Expect further updates on this useful business tool.