The Beta2 bits of the WinFX Runtime Components are now available. This includes the RC0 bits of WCF.

Get it here:

http://msdn.microsoft.com/windowsvista/downloads/products/getthebeta/

 http://www.microsoft.com/downloads/details.aspx?FamilyId=4A96661C-05FD-430C-BB52-2BA86F02F595&displaylang=en