It can be difficult to decide when it is the right time to deploy an Intranet, particularly because of the hype that surrounds the topic. As in most cases, it is more helpful to look at the benefits to the business rather than be swayed by the hype.
The main business advantages come when a company or organisation is large enough that some of the following are useful (typically when you don’t know everyone in the company, or there are shift patterns / geographical spread):
directory lookup including more than just the Active Directory type information, listing areas of expertise, etc
news group / forum type features for sharing expertise or solving problems
information resources that are updated relatively frequently, such as HR, quality system, standard purchasing list (there can be a problem here of staff not being aware of the latest HR policy though)
useful applications, perhaps a purchasing system with workflows, linked to the purchasing list
where some internal communications are relevant to a subset of the staff (perhaps a division or special interest group); it can be more helpful to have this available on a “pull” basis by the user, rather than a “push” email to all
email summaries can be sent at user selectable intervals of what’s new and what’s changed with the detail on linked pages
as an extension to document sharing, particularly when SharePoint is used
Considering these can avoid investing in a white elephant that no one looks at.