You are looking for "cool season" crops; in addition to what Om said,
include: cold hardy lettuces, endive, arugula, claytonia, mache.

For my zone, this would all have had to be started back in mid-late
August to have anything worthwhile now to Dec.

If you have carrots already planted, mulch 'em and they are supposed
to not freeze (stay pull-able) and get tastier as the cold turns their
starches to sugar..