One solution is to bounce the flash illumination from a white ceiling or wall. Some Speedlites have a tilting head that allows you to aim the flash at a ceiling. A few Speedlites add a swivel head, so that the flash can also be reflected from a wall. Autoflash exposure remains active – sensors in the camera compensate for the illumination lost by reflection.
Reflecting the flash from a wall or ceiling is better than direct flash, but does not give you complete control over the illumination. For this you need to move the Speedlite away from the camera, turn it away from the subject and bounce the flash from a white nylon brolly on a stand. Several current Speedlites offer wireless flash control. With a transmitter on the camera, one or more off-camera Speedlites can be controlled automatically for correct flash exposure.
Multiple Speedlites give you total control for indoor portraits. A typical setup will have one Speedlite and brolly to the side of the camera giving soft illumination to the subject. A plain reflector might be used on the other side of the camera to reflect some illumination back into the shadow areas. A second Speedlite can be used behind the subject to illuminate the background, or the back of the subject, giving a rim of light around the hair. This backlight separates the subject from the background, giving depth to the image.
Visit EOS Adventure for a guide to the full range of Canon Speedlites.