A couple of more outside ideas. A foggy day, zoom in tight on your subject. With the sun low in the sky, have your subject block it out as you shoot directly at it. In general have your shadowed subject in front or backed up against any bright background. As suggested above, meter the sky around the subject and lock it in when you aim at the subject. Experiment with bracketing the exposure.
Here is a n explanation from an article by Vounes Bounhar in the digital Photography Magazine:
"To determine the necessary exposure for a backlit scene, I prefer to use manual exposure. This allows me to take the reading on the appropriate part of the scene, then recompose to frame my subject as I wish without having to worry about locking exposure or variations in meter readings from dif- ferent parts of the scene. There are two ways to go about taking the meter reading. If you want to take guesswork out of the equation, I suggest using the spot metering function of your camera, which you then point towards the area you want to expose for (i.e. if you want a silhouette, point it towards the brighter background, conversely, if it is a high key effect you are seeking, take your reading off the subject directly). Once your exposure is locked in, recompose and shoot. Alternatively, if you
are more comfortable with the matrix/evaluative metering modes, you can simply take a reading on the entire scene, then overexpose by a few stops to obtain a high-key photograph, or underexpose by as many as 3 stops to obtain a silhouette. "