Kurt Shintaku's Blog

This is a heck of a site.  It effectively documents what ports are necessary to expose a specific application service through a firewall or filter. 

• Service overview and network port requirements for the Windows Server system
  http://support.microsoft.com/kb/832017

This is a living document and is updated regularly to include new and updated products and services.  Here’s a sample list of services that are currently listed.

• Active Directory
• Application Layer Gateway Service
• ASP.NET Slate Service
• Certificate Services
• Cluster Services
• Computer Browser
• DHCP
• DFS
• DFS-R
• Distributed Link Tracking
• DTC
• DNS
• Event Log access
• Exchange Server
• …