I was planing the same, my average first frost date is 21st October. Subscribed to this thread, looking forward to see suggestions.
My list for fall garden (not finished) looks like this:
- Lettuce (head)
- Peas
- Radish
- Carrots
I am not sure will I be able to harvest peas however, but anyway even if I don't they should be able to fix soil with nitrogen before frost kills them.