I recommend two excellent books for learning WCF.
First, you need the WCF Bible - "Programming WCF Services" by Juval Lowy. This is THE book for WCF - Lowy covers just about everything with very thorough detail. This is a pretty deep, technical book. You'll want to take it slowly, at first at least. Be sure to get the 2nd edition - it covers VS2008 SP1.
Lowy also has built an excellent library around WCF that's a companion to his book. It's called ServiceModelEx - you can find the source for it here. It really helps to have the book though!
Second, I suggest taking a look at "Learning WCF" by Michele Bustamante, also by O'Reilly. This book hasn't been updated for VS2008 and .NET 3.5 but there's still a wealth of good information here. This book is more like a step-by-step tutorial. It really helped me get a handle on just what WCF is and what it can do.
Beyond that the best advice has already been given. Code your butt off. I can't stress this enough. WCF made almost NO sense to me until I started coding. Go through tutorials. Pick something fun to turn into a component and see how many different ways you can access it via WCF.
Good luck and have fun!