I just took a short walk around the neighborhood and noticed a number of places are open.
The natural organic market on 84th/85th and 37th is open 10-5.
Espresso 77 is open til 8 pm.
Not sure of hours but I also saw the Kim Brothers, Mango Rico, the 99 cent store on 83d and Roosevelt, the fruit market between 83rd and 84th on 37th, Caffe Bene and Lemon Tree are all open. I'm sure there are others or ones I didn't think to look at.
Please add to the list if you feel so inclined.
Merry Christmas!