From an article "Off-camera flash photography" pg. 60, EOS Magazine, January-March 2015
"Taking a Speedlite off-camera means that you need to find a way to trigger the flash to fire in synch with the shutter being opened. There are several methods available.
The most straightforward is to use a Canon Off-camera Shoe Cord OC-E3. This is a fully dedicated cable that links the camera hotshoe to the Speedlite flash retaining full automatic controls and settings. However, the coiled cord is only 60cm long when fully stretched, so there are limited options for using the flash creatively.
The earlier Off-camera Shoe Cord 2 is similar, but lacks the moisture and dust resistance (with weather-proofed cameras) of the current cord.
The original off-camera shoe cord was designed for the Canon T90 camera and Speedlite 300TL and is not compatible with EOS cameras.
Canon also offers a Speedlite Bracket SB-E2 that comprises a flash bracket and the OC-E3 cable together. This allows the Speedlites 430EX, 430EXII, 580EX, 580EXII and 600EX-RT to be securely attached and complete automatic functions to be retained."