An Intranet is a web site for internal use. It typically is not visible at all to the Internet, so more private information can be presented to a variety of internal users. It can make a difficult development situation into an easy flow. The trick of it is to create a centralized location for information relevant to the development process. This can include any or all of the following:
My experience with an Intranet is that you don't know what it will be good for until you have it. The most difficult part of it is keeping it relevant and up-to-date. Each person who is involved needs to watch that they don't overwrite something that is being edited at that moment. It will become more valuable the more you use it. I don't bother with too many images or complex markup simply because the presentation is less vital than the information itself. My time is much better spent making sure that the information is relevant to my day-to-day activities.