Photodoto » Blog Archive » Shooting in overcast conditions:

Overcast conditions aren't typically what photographers talk about when they discuss beautiful light. The "golden hour" (dawn and dusk) is only golden if you can see the sun. But overcast conditions have their advantages as well and you can still take great photographs under a gray sky as long as you choose your subjects carefully.

I find it hard to get motivated to go out shooting on cloudy days. Probably something I should make more of an effort about...