Color spotting is a cool technique to show case an element of a photo. Black and white photos a very unique but I have never really been a huge fan of B&W. With the color spotting it adds a touch of color that spices up the whole photo. It is a very easy task in photoshop. All you do is select the part you want to be in color and add a black and white mask. Once you do that, invert the mask and your done. Although this is an easy task it's one of my favorites. 
Photoshop CS5.5
Canon 600d

Color Spotting.