On G.O.L.D is 'Sitcom Does Christmas'. It's very Royle Family centric (as it's hosted by Ricky Tomlinson, and Ralf Little is talking to him about stuff on it), but showing bits from other shows of course. Apparently it takes them til up to about 20th November to write a special (days before filming), guess it was a little TOO late this year.
Only Fools and Horses 'Christmas Crackers' and 'Thicker Than Water' are fantastic, though most of their 80s episodes were good, IMO.
Royle Family - 1999 and 2000 were great. Thought last year's one was a return to form though.
The Office Christmas Specials - More so episode 2. Warm and brilliant, and really spoke to me at the time as a) It was my first Christmas in full time employment in and office, and it amused me greatly how accurate it could be and b) I'd literally got with a girl I'd like for ages (like Tim did, though mine wasn't a work colleague). And a re-watch last year confirmed that they're still awesome. Showing the department store from Father Ted too, with the guest priests saying bits about the episode.
Gavin And Stacey - A fun and sort of realistic Essex Christmas. One of the best G&S episodes. Also, as Dennis Pennis said they've only done one, so it makes it a bit more special than others.
Plan on seeing Father Ted's special and the four dinners and Nativity specials of Vicar of Dibley this year as they always get overplayed and I have avoided them these last couple of years.
Going to watch Blackadder's Christmas Carol (a yearly must), Men Behaving Badly (the actual Christmassy one) too. Will try to see Dad's Army and Porridge when they're on TV.
Away from sitcom, I might watch a couple of Doctor Who specials if I have the time. Particularly last year's Christmas Carol, and Tennant's first episode.