Shooting digital in cold weather is a little different from traditional photography. Here are a few tips:
Cold sucks the energy from your batteries and can hinder the performance of some memory storage devices. It helps to the camera warm inside your jacket, with the lens covered, until you are ready to shoot.
If you thought it was difficult to change film outside in icy-cold weather, try changing one of those tiny memory cards. To make those delicate cards easier to handle, try wearing two pairs of gloves, with the fingertips of the inner glove cut off. Thin, high-tech gloves also work and are available in most winter sport shops. And avoid prolonged contact between frozen metal parts and bare fingers, noses and cheeks. Prying flesh from frozen metal is no fun.
Keep falling snow off your camera by putting it into a zip-lock bag with holes cut out for the lens and viewfinder. And to prevent fogging, dont breath on the lens or viewfinder.
Avoid condensation by letting your camera warm incrementally when you go indoors, and make sure to brush snow off all the equipment before entering a heated room. You can also seal your camera in a plastic bag, which prevents condensation from forming.
If you do get ice on the lens of your camera don't scrape it! You're likely to scratch the lens. In cold weather, ice can get very hard and forcefully scraping it can scratch the lens. If the ice is thin, hold the lens so it faces the sun and the sun will sublimate (evaporate) the ice from the lens. You can also try warming the lens in your pocket or with your breath and then wiping the water off.
Some links:
http://arttech.about.com/gi/dynamic/...ldtemps01.html
http://www.mongeese.org/photos/tips/