I am totally in love with my new ballet flats purchased at Target!  They are so warm because of their fleecy lining inside the shoe, yet not too warm once inside a heated building.  The lining also does not show, so they still just look like cute regular ballet flats.  I highly recommend these comfortable and warm, not to mention cute!!, shoes :)  They come in brown and black… you can find them online at Target.com, or in a Target store near you.