We've all heard of the "magic hour" - that early morning and late afternoon time when the light is warm and slanted. It's perfect for landscapes. But what do you do with an overcast day? Have you really lost the opportunity to make great shots?
No, of course not. you just need to change your approach. Overcast days are great for fall foliage. Just keep the sky out of the frame. They are terrific for animals, flowers, etc. All kinds of macro shots benefit from the softer light of an overcast day.
Of course, true stormy skies are different - they can be very exciting. What you don't want to try to deal with in post-processing is a blank white sky. That's what you will get if you shoot a landscape on a flat overcast day.