I would start to write WPF and Silverlight 2D game, i would to find some game engine library,the only one i found on google is FarseerPhysics ( http://www.codeplex.com/FarseerPhysics) and seem quite good. But is there any other recommend for starter?
And one more question is is it any alternate software of expression blend for create Silverlight UI?
See also the Physics Helper for Silverlight, WPF, Blend, and Farseer.
Kaxaml is a lightweight XAML editor with split view.