Jack points to this article about developments on the intranet front by Gerry McGovern. Emphasis so far is on Management buyin and support being supercritical to the success of any serious intranet effort. I think this applies regardless of how big or small the organization is.
I think this is even more critical if you are going to add social networking tools like blogs and wikis that are different into the intranet space.
I am interested in experiences that people have had introducing Wiki and Blogs into the intranet space. If anyone has a secret hoard of experience /reports from the front lines, please post them in the comments. I'll summarize them here.