Other than long underwear, the best winter invention is disposable body warmers! 使い捨てカイロ（つかいすてかいろ）in Japanese, these little packets of heat are great in cold weather. They're apparently made of carbon and other things and are bio-degradable. One packet lasts the entire day. I may go through a lot this winter! It's about 300 yen for a packet of 10.
edited: weird, random span tags sneaked into my post. The dangers of cut & pasting text.