LCD and Viewfinder
Canon 400D has a Fixed Type 2.5" LCD screen with a resolution of 230k dots. At only 2.5", the screen is on the smaller side and 230kdot resolution is lower than most of the recent models in this class.
400D has a built-in Optical (pentamirror) viewfinder. The viewfinder has a coverage of 95% and a magnification ratio of 0.5x. 95% coverage means that what you see in your viewfinder while shooting will slightly be different from the actual image.
Max Shutter speed
Canon 400D can shoot continuously at max speed of 3 fps
and has max shutter speed of 1/4000 sec
400D has a built-in flash, and it also has a flash shoe to mount your external flashes too.
Canon 400D features a Phase Detection autofocusing system. The AF system has 9 points to choose from.
Unfortunately Canon 400D doesn't have Video recording ability.
Connectivity and Storage
Canon 400D has a USB 2.0 (480 Mbit/sec) port to connect your camera to other devices.
Canon 400D Features Compared to Main Competitors
You can download Canon 400D's User Manual here