Assume from the get-go that your Intranet is going to become mission critical. Ask yourself, your boss and the business managers some hard questions so you don't get sucked into the hype vortex. It's a question of ownership. Content is typically in the realm of the individual department. Whoever owns them pays for their upkeep, and while Intranet start-up costs are low, maintenance and ongoing development won't necessarily be so cheap.
Professionalism is important for internal applications, too.
Define an approval process for putting up content, as well as procedures for keeping content current. Users with a little HTML training can maintain the Web site content or IT can maintain it as a for-fee service. Web application development tools are in their infancy. Netscape is coming out with extensions faster than anyone can document them. Be willing to rewrite your Intranet applications significantly every few months to accommodate changes in APIs or extensions.