From Dave Relyea's blog, Pixel Snapping in Silverlight as an attached behavior:
http://blogs.msdn.com/devdave/archive/2008/06/22/Using-an-Attached-DependencyProperty-to-Implement-Pixel-Snapping-as-an-Attached-Behavior.aspx
PingBack from http://blog.a-foton.ru/2008/07/great-example-of-an-attached-behavior/
Also check out this blog by a guy named Rudi:
http://dotnet.org.za/rudi/archive/2008/03/27/keeping-track-of-open-windows-in-wpf.aspx