Cityographer lets you instantly create a city map and details (residents, store inventories & prices, etc.) You can have the program do it all in one step, or run it in a step-by-step fashion and edit the map and details as you go. Everything created is always completely editable.
Currently the software is focused on medieval/fantasy cities, but data and graphics for other genres are coming soon! In fact, futuristic and modern graphic sets are already available.
The software runs on top of Java, which makes it Windows, Mac and Linux compatible. (And even some other systems.)