Frank has been blogging about Tim Sneath's series on Great WPF Applications.
Check em all out here.
I'm gradually getting through them.
There is one that has got my attention (read blowing me away). The German based Otto online shopping app (direct link).
This thing is amazing and is setting the standard for online shopping experiences.
It's in German but isn't too hard to figure out - a testament to great design.
Have a play.