This is a free tileset of city streets and grass areas to help you lay down a foundation of city roads for any top-down or isometric style project. If you're going to use this for mobile development make sure to atlas all of these 256x256 textures onto a couple of 512x512 textures or maybe a 1024x1024. NGUI, Sprite Manager 2, and several free sprite tools exist for the Unity engine that process texture atlases.
I would also suggest checking out the Modular City Kit video on my Youtube and grabbing the modular buildings. These modular buildings would work awesome placed on top of these tiles.
Download link via Dropbox is in the Youtube video description:
Some images to preview:
And a Unity webplayer to to just drive around a snapped together set: