I recently picked up Seven Cities, a book in the Penumbra d20 line that Atlas Games produced.
I haven’t read the entire thing, but so far I like it. A lot.
It has seven cities of various sizes – from thorp to large city. The detail is finer on the smaller towns, of course, but they did something rather smart in producing this book. Each city builds upon the one smaller than it… so a location in the torp might show up in the hamlet, small town, small city, etc. This allows for pretty significant detail even for the larger towns. It was clever. I like clever things.
I like them even more when I pick them up on sale for $5.
A full review of the book can be found on RPGnet.