Do you have some low-contrast images in your collection? Low contrast photographs are often characterized by soft textures (or none at all), even lighting that eliminates harsh shadows... attributes that result in a narrow histogram distribution.
Jay's shot (below) from White Sands National Monument in New Mexico was taken on a heavily overcast day. Those heavy clouds filter and scatter the light so that shadows are all but eliminated. Minimalist compositions work especially well in conditions like these, so he positioned the camera to remove all distractions from the frame. The smooth curve of the sand dunes, the subtle color tones, and the simplicity of the point of interest... subtle imagery and subtle light go hand in hand.
Here's another example. In his case, heavy fog obscured the mountains in the distance. A shot across Maroon Lakes in Colorado shows the gradual reduction of contrast that results from conditions like these. Notice how clear the foreground appears. Contrast is much higher in the foreground, but as the distance increases, contrast decreases. The result is a moody image with a heightened sense of distance and depth.
Overcast days call for a different mindset. We won't be getting any spectacular sunbeams, crazy colors, or incredible cloud formations. Instead, we need to pay attention to form and texture. When color isn't interesting... when it doesn't add anything to the image... it's time to start thinking in monochrome. This shot of Cannon Beach in Oregon is a perfect example. The sky was a dull grayish blue, and the blue tint to the light left the sand looking lackluster. On the other hand, the subtle beauty of the landscape hadn't gone missing! A place like this doesn't need a blazing sky to make it breathtaking. I took this shot knowing I would convert it to b&w. The emphasis is on texture, form, and tone - and color would be a distraction.
Overcast skies call for creativity. Don't pack up the camera and head home! Pull out your gear, change your mindset, and work the subtle light for all it's worth!