Photo Black & Color is an amazing free software that lets you partially desaturate your images. This results in applying grayscale to some areas of your images, and leaving other areas colored. This makes your images look really amazing.
It is extremely easy to use Photo Black & Color. Open the photo that you want to desaturate. Then, select the colors in the photo that you want to keep. This can be done easily by using the built-in pipette tool.
Once you have selected the colors you want to keep, just start the Desaturation process. Photo Black & Color will convert the colors that you did not select to Grayscale.
Photo Black & Color is really easy to use, and can give extremely good results. Try to use photos that have one main subject, and background colors different from the main subject.