If this is an area of interest to you (and it probably should be), then I strongly recommend you read two posts from Jeremiah Owyang and Neville Hobson.
In List of enterprise microblogging tools: Twitter for the intranet, Jeremiah has started a list of vendor offerings in the area (currently standing at eight). Well worth watching I think.
Neville takes one of the offerings, Yammer, for a test drive in Twitter for the enterprise from Yammer.
Like blogs, wikis and other social software that has gone before, I advise caution. Make sure you know what you want from such tools (and also what you need in terms of security and control) before diving straight in.