In the photo you put in the question, note how the foreground is extremely underexposed. This is because the exposure metering was made relative to the snow. However, if you set the snow to the standard exposure, you will get a "dark", gray snow. You need to add about 2 stops with Exposure Compensation (or use manual mode) in order to get a bright white snow.
A polarizer can certainly help by eliminating some of the specular reflections from the snow, to make it more "uniform".
Update: If you wish to shoot people on a snowy background, you can easily run into the problem of overexposed snow or underexposed persons. Except for using grad-ND filter, like mentioned in the other answers, for reducing the brightness of whatever is above your subjects, you need to find other, smart ways to equalize the brightness levels.
Your options are to try shooting when the person is facing the sun, to use large reflectors or to use active lighting like (off-camera) flash.
Another link on the subject: How to cope with high contrast?, and see Matt's answer.
(*) I am assuming you know how your light meter works and how to use it.