One of my favorite designers, Celso Gomes has just launched, "Nibbles: Snack tutorials for hungry designers". Eventually it will include WPF samples but for now, is focused on Silverlight!  Not a designer you say?  You should still check out his samples.  Celso is an incredibly gifted designer and inviting others to submit.  He has a blog set up too for feedback and updates.  Nibble away.