"Intranet" should just be another word for integrated internal information tools. There are already lots of them in your company. I can pretty much guarantee that. But knowing where to find them, how to use them, and getting them to interact with each other is a big task. That's what I mean. A company intranet should start by bringing together, standardising and advertising all the useful tools your company already uses to run smoothly.
Mokalus of Borg
PS - In my experience, most companies use it for haphazard document control and the occasional internal blog post.
PPS - And sometimes a staff directory if you're really lucky.