Well I hate to be known as Blender-Script-Man but there is a blender (python) script that creates city blocks (although when I say "block" I do mean block).
Here's a link to the Blender script list effort
over at elysiun.com. I'm not sure if the city block script is in this list (I don't think it is) but It's in that forum.
And a reminder: If your looking for the latest and greatest go to the fourms at http://www.blender.org
and download the latest daily build (Yafray, some additional features for the loop subdivide, bug fixes, etc.)