LCD and Viewfinder
Canon 1Ds MIII has a Fixed Type 3" LCD screen with a resolution of 230k dots. Both the screen size and the screen resolution is up to the standards of this class.
1Ds MIII has a built-in Optical (pentaprism) viewfinder. The viewfinder has a coverage of 100% and a magnification ratio of 0.76x. 100% coverage ensures that what you see in the viewfinder while shooting matches exactly what you will get later in your image, helping accurate framing your shots and minimizes the need for cropping images later.
Max Shutter speed
Canon 1Ds MIII can shoot continuously at max speed of 5 fps
and has max shutter speed of 1/8000 sec
Unfortunately 1Ds MIII doesn't have a built-in flash but it has a flash shoe for mounting external flashes.
Canon 1Ds MIII features a Phase Detection autofocusing system. The AF system has 45 points to choose from.
Unfortunately Canon 1Ds MIII doesn't have Video recording ability.
Connectivity and Storage
Canon 1Ds MIII has a USB 2.0 (480 Mbit/sec) port to connect your camera to other devices.
Canon 1Ds MIII is powered by a proprietary battery which provides a shooting life of 1800 according to CIPA standards.
Considering that the average battery life of DSLR type cameras is 883 shots, Canon 1Ds MIII has a good battery life for its class.
Battery Life Comparison in Pro DSLR Cameras
Nikon D3X with its 4400shots is the model with longest battery life among Pro DSLR cameras. Check the comparison of Canon 1Ds MIII vs Nikon D3X or take a look at Longest Battery Life DSLR cameras list.
Canon 1Ds MIII Features Compared to Main Competitors
You can download Canon 1Ds MIII's User Manual here