Over time I have found some Microsoft team web sites to be very handy. These include the Microsoft Exchange Team, the IIS team and most recently the Open Source Software lab team. Below I have the links to these sites so you can check them out and add them to your favorites.
Port 25 The Open Source Software Lab at Microsoft
Microsoft Internet Information Services Homepage
Also if you have sites that you find useful please leave them in the comments so I can addt them.