I have been using WPF for a bit, written about LINQ, but decided I should explore some of the other .NET 3.0 stuff.
To this end I have create a WPF / WCF chat application using all the good WCF stuff like callbacks etc etc.
You can see the application at codeproject or just follow this link.
Anyway it looks like this, oh I got a prize for this. People liked it.