PicFX is an add-on for WP7 that lets you change a photo to black and white, sepia, adjust tints, brightness and contrast and then save the changed image as a new photo (so it doesn’t save over the existing image). Here it is in action showing just black and white and sepia effects that are just one click:
The entire source code and more details on the project are located here. And good news – advanced effects are coming soon. In other worse – photo editing is coming soon to WP7!