Open in southern Maine on Christmas Eve/Day?
The Ramp is open Christmas Eve (and I'll mention that I'm not trying to drum up business for them, since I've posted about them before! I just enjoy going there when I'm in town) http://www.pier77restaurant.com/
I've not been to On the Marsh in Kennebunkport, as we usually are doing beachy visits to Maine with children, but I've heard good things, and I noticed they were open for Thanksgiving Day. http://www.onthemarsh.com/index.html
On the Marsh
46 Western Ave, Kennebunk, ME 04043
Thanks, those were actually the first two places I originally checked. York Harbor Inn is closed Christmas Day (well, open till 6 PM but not serving meals, just donated food in the cellar for people who are alone or have no place to go), and Warren's is closed both days. :(
York Harbor Inn
Coastal Route 1A, York Harbor, ME 03911