The January CTP of WinFX (which includes WCF) is available on MSDN online. Note some good advice on installation from Charles Petzold.
WCF and it's pal Windows Workflow Foundation were anointed with GoLive licenses. The runtimes associated with these can be downloaded here.
WCF gets a home on the web at www.windowscommunication.net.
Don't Forget: www.acehaid.org
