I wish I knew where I picked up this tip, so I could credit the wise person who thought of it. If your kids spend a lot of time outside in the winter, then you've heard their complaints about cold wrists -- that pesky gap between jacket sleeve and mitten or glove. Try this:

Take an old pair of knee high socks and cut the toes out, as well as a small hole in the side for the thumb. Essentially, you've made a cheap pair of fingerless gloves. Have your child put them on before their don their jacket, pulling the sock up to the elbow. Then add mittens. No more cold wrists!

The idea has worked like a charm at my house, and extends out outdoor playtime significantly.