Not sure if this was posted, but this is AWESOME reference for modular environments. There's a LOT of images and instructions deep in here, be sure to look around (projects page) http://www.hirstarts.com/
Check out Kevin's post about GOW2 bricks. Gears of War 2 modular modeling More here. http://wiki.polycount.com/CategoryEnvironmentDesign#Modular_Design_and_Workflow