Dusk is my favorite time of day. It's when the sun has set beyond the visable horizon but the sky is still light - it starts with sunset and ends with twilight.
I live in a valley that is sourounded by hills on all four sides, so my dusk is somewhat longer than someone's who, say, lives on a prarie, becuase the sun here only has to set below the height of the mountains to the east - the tallest ones in my valley - rather than set below the level curve of the world. Here the foremost part of dusk is still quite bright; enough that you could be out walking in a park - which is, often, precisely what I do - but not so bright that everything looks white washed, as sometimes happens during the brightest part of the day. Rather, every colour looks deeper and richer and really just, in my opinion, much nicer.