Gray is totally the next black. Or at least that is what it looks like based on all the lovely manicures I see on elegant women in the New York subways. I am particularly taken with the gray and silver offerings at Essie. Essie polish is sold at my local Duane Reade but can you find their full selection online here.
I am partial to the top left color, called "Chinchilly", which I used last night. It is a shimmering combination of gray and taupe with a hint of lavender thrown in.