My post on sterile dungeon maps touched on this slightly but I really must wonder why we keep churning out flowchart dungeons? So many dungeons are nothing but elaborate flowcharts, you can tell by the empty corridors and boxes those corridors lead to. Corridors are this ridiculous empty space in many dungeons put something in the corridors.
Think about the corridors you are exposed to in real life and what roll they serve, think about the activity they support and what you'd notice going on within them. Why would dungeon occupants virtually ignore corridors and what's going on within in them outside of the occasional wandering monster or random encounter? Think back to school, how quickly would teachers,students, and staff notice trouble in the corridors if it happened when classes were in session? Think of how full the corridors are between classes in a school or during a shift change in a factory, that's the sort of stuff that should be going on in your dungeon unless it's an abandoned tomb.
Dress up those corridors, have the locals pay attention to them, and determine how busy they are and a dungeon is going to grow into more then an endless repetition of floor tapping looking for pit traps (not a great place for traps in a active complex), kicking open doors, and fighting with the monsters on the other side. Dungeons don't have to be flowcharts.