If you want to see how the WCF works and go through main scenarios of writing, securing web services, you can check out nice workshop.

http://cid-dcb2904f175f67aa.skydrive.live.com/embedrowdetail.aspx/Public/WorkshopDocuments/WCF-WindowsCommunicationsFoundation(.NET3.0)

If You’re lazy doing the “labs”, it might be enough to read PDF’s through to get the idea.