As much as I like the individual buildings we usually think about when talking about modular building, I'm beginning to think that complete city blocks are sometimes more appropriate for group layouts. There's something special about being able to point to a coherent section and say "I built all of that". Take this block, for example:
|Photos courtesy of LUKY'S 1987 LEGO CREATIONS's flickr photostream|
That's two opposite corners of the same city block.