Leveraging Existing Enterprise Technology
Some corporate environments already have existing enterprise solutions in place for e-mail communication and management of business process. The most-deployed products in this category are Lotus Notes and Microsoft Exchange. Both of these platforms can be extended to some degree to create a proper intranet that runs parallel to existing systems and leverages existing technology (such as user authentication).
Neither of these systems are thought of very favorably in the development community because the intranet extensions were generally an after-thought to the products' development. That being said, both IBM and Microsoft are working on improving this (through WebSphere and .NET, respectively) and it might be worthwhile to explore this option if the system is already in place. It would allow you to centralize your processes (probably running on the same machines) and have current IT staff extend their responsibilities to cover these areas, too.