How would you go about to implement a docking toolbox windowing system as seen in Expression Blend where you can dock toolbox windows in a lot of ways beneat each other, ove
There's a great WPF Docking Library someone has published on codeproject.com, that has the functionality you're looking for.
I used it myslef once, and i got it going pretty smoothly.
Check it out here : http://www.codeproject.com/KB/WPF/WPFdockinglib.aspx