Well, how much are you looking to spend, are you open to buying clothes from eBay, and if so, what size are you looking for?
I have a Citizens of Humanity jean skirt from two years ago that I love to bits and pieces but they no longer make it. I ended up buying a backup skirt (the exact same one) just in case!
If you're in a pinch, I would try Abercrombie... Most of their clothes just scream ABERCROMBIE to me though. It is rather hard to find a nice denim skirt...
Normally I won't even look at anything but designer denim, but I actually bought a super cute denim skirt from Old Navy about a week ago. It was only $24!