Ralph Squillace posted an walkthrough entry of how metadata publication (MEX + WSDL) is enabled in Windows Communication Foundation. Besides discussing the configuration aspects, he also briefly touches on how those aspects affect the runtime behavior.

This came at a perfect time for me because I spent a few hours yesterday going over the System.ServiceModel assemblies with reflector trying to understand how it was that the metadata endpoints get hooked up to a service, so this helps a bit. I still need to look closely at a few issues before I understand what's going on well enough to try at something similar I've been wanting to play with...

Ralph has also been writing some samples about Sessionless Duplex Services here and here which are quite interesting as well.