Use Your flash
I'll admit that you have to be dedicated to carry a reflector around. A more convenient solution might be to use your [[xref:http://www.pcworld.com/article/112660/digital_focus_master_your_cameras_flash_modes.html|digital camera's fill flash|Digital Focus: Master Your Camera's Flash Modes]]. If you're photographing a subject that's fairly close to you — say, within about 10 feet (3 metres) — make sure that your camera's flash is enabled, and allow it to "fill in" the shadows.
Using the fill flash is a great way to fix high-contrast scenes, but remember that it works only with nearby subjects. The flash units built into most digital cameras have a short range, so they can't do anything to a sun-dappled field 15 feet (4.5 metres) away. For that sort of muscle, consider adding an external flash.