During the winter I wear hiking boots with two layers of socks (one wool and one thermal). This works pretty good down to about 0F. Below zero and I just assume I'm going to have cold toes after about 4 miles. They don't get any colder than if I'm out shoveling in the same temps for the same time.

I'm sure the chemical warmers would work, but frankly I'm too cheap to spring for those.