What is your favorite discovery for commuting in colder weather?

It'll be in the 40s tomorrow am, and I know it's going to get colder than that.

I've got a good windbreaker and cool weather cycling gloves. An ear warmer wrap that I've used before. Thought I would go with running tights.

One thing I've noticed before in colder weather cycling is that my core stays plenty warm; it's the extremities that get chilly.
Other than thicker socks, I don't have any great ideas for the feet.

As of now my plan for the winter is to say I will do cold, potentially very cold. I will do rain, but only above 40 degrees. Not going to mess with cold rain, snow, or ice.