This winter we grew spinach, radishes, lettuce, arugula and a big parsley that I transplanted into it at the end of the season. A couple of things to remember: You have to take the cover off and water things once in a while - a couple of gallons of lukewarm water is all I need every few weeks. Also, if you get a lot of snow, you have to scrape it off every few days to let the light in.
This is a photo of the cold frame on December 7th. It had survived several days of around 0 weather. Things aren't looking so lush today - it is January after all, but I still have plenty of greens.
More photos later when we get Adobe back up and running and a new battery for the camera. Sigh.