Windows Communication Foundation Links

WCF - http://msdn.microsoft.com/en-us/netframework/aa663324.aspx
(.net Framework Developer center, central resource for all things WCF)

WCF 3.5 samples - http://msdn.microsoft.com/en-us/library/ms751514.aspx

WCF 4.0 samples - http://msdn.microsoft.com/library/dd483346(VS.100).aspx
(good resource to learn the basics by playing with samples)

WCF screencasts - http://msdn.microsoft.com/en-us/netframework/wcf-screencasts.aspx

.Net endpoint blog - http://blogs.msdn.com/endpoint/
(Blog by the .NET and AppFabric teams about WCF and WF development, deployment, and management)

Bug report/ Feature request/ Feedback to the product team - https://connect.microsoft.com/wcf
(There are useful resources mentioned at the bottom of this page as well)

Detailed WCF security guidance - http://www.codeplex.com/WCFSecurity

Detailed debugging using WCF tracing - http://msdn.microsoft.com/en-us/library/ms733025.aspx