I strongly believe firms should exhaust all the out of the box features of MOSS before even thinking about development. A POC should run with only out of the box features and a board should decide on a limited number of additions only after MOSS is ready to roll in the organisation. This blog post shows how much you can do out of the box with MOSS.
An Intranet page using Portal Definition with Web Content Publishing. Much of the information on this page is coming from RSS feeds, meaning the page is a portal integrating key information from many wikis, blogs, and other areas in a single space. I have often used SharePoint to to track many rss feeds on the web.
Here is the killer app! A project site with document management and security control, even a gantt chart all with out of the box features of MOSS.
Wikis and blogs as well. Enterprises should take the lead from low budget private users who have taken free tools like blogger and wikipedia and managed to collectively make the largest collections of data in history. Use established tools and concepts like blogs, wikis, chat groups, and news pages rather than spending time and money trying to re-invent the wheel.