Recent versions of Photoshop have a Targeted Adjustment Tool accessible from the Properties panel of the Curves and Hue/Saturation commands.
In the Adjustment Layer Curves command panel, it is the hand in the top left of the panel that contains a two-sided arrow. Selecting the tool and then dragging it up over a portion of the image, lightens all of those pixels that have the same tonal value anywhere in the image. Dragging it down darkens pixels of similar tone values. The short video below demonstrates this tool. Watch how the shape of the curve changes.
The Hue/Saturation command also has a Targeted Adjustment Tool. Dragging it over to the right over a portion of the image will increase the saturation of similar color pixels and dragging it to the left decreases the saturation. Control-dragging the tool changes the hue of the pixels.
In a Black and White Adjustment Layer, dragging left will darken the pixels of similar colors and dragging to the right will darken them.
If you want to be more selective with your changes, you can make a rough selection containing the area in the image you want to adjust.