Even though I like the golden lighting of sunrise and sunset for photography, overcast conditions produce extremely soft and very flattering light. The contrast is low and the colors turn out to be much more brilliant than you'd expect.
The soft light of overcast is my favorite type of lighting for outdoor portraits. And this applies to outdoor portraiture of any kind - kids, animals, families, and other subjects too, such as this costumed model at Carnival in Venice, Italy.
Additional info: Jim Zuckerman teaches a number of online photography workshops - including Techniques of Natural Light Photography - at BetterPhoto's digital photography school.