Rick Barraza from Cynergy has been doing some great work showing how to use WritableBitmap and PixelShaders to create some very interesting effects in Silverlight. Check out both
his recent posts Advanced Render Techniques with WriteableBitmaps and
Fluid Dynamics in Silverlight.
Ward Bell demonstrates how to
disable image-based buttons in LOB apps with a Grayscale Pixel Shader in WPF. Not only does this save you from twice the image assets to maintain, but its also very simple to do. And you feel cool, because you're using Pixel Shaders.