Photo Shader is a decent little photo editor for your Windows Phone. The app has a healthy amount of filters and effect to apply to existing photos in your Pictures Hub or new images captured with your Windows Phone camera.
Layout is simple and clean with most filters/effects having setting to fine tune the application. When you first select a photo to edit, cropping tools will appear to let you crop and/or rotate the image. From there, all you need to do is apply your effects and save when done.