Broadly an intranet is a website, by another name. Technically it is absolutely a website but with the additional benefit of control over how users view it.
A successful intranet is generally defined by its internal uptake by the company providing it. There are a number of software solutions that have been through all the pain of devising how staff can interact with company information, standards and each other. The fundamental key to it however, like all the other digital touch points, is working out why and for whom it being developed in the first place, which can be easily overlooked when it is an internal project.
There are also many lessons being learned in the Intranet community from the Web 2.0 disciplines. Think how people communicate with each other on say, Facebook and then apply that thinking to your internal communciations. The results can be interesting! And the software to do it is available now.
Whatever your need, we can help you refine the initial thinking, find the best way to develop it technically and make it an ongoing success.