Science Fiction Christmas Stories

I read Connie Willis's anthology "Miracle and Other Christmas Stories" every December to get me in the holiday mood.

My favorites are "Newsletter," which is a humorous story about a woman trying to fend off an alien invasion at Christmas time, and "Inn," in which a woman helps out a homeless couple on Christmas Eve only to discover that there is a lot more to them than meets the eye.  It's fun to read science fiction Christmas stories as it is my genre, and Connie is one of my favorite authors.

I just discovered that I have an Amazon gift card left over from last Christmas that I ought to spend, so it's time for a little holiday gift exchange.  Who are your favorite authors?  If you know of anyone else who writes scifi Christmas stories, great, but it doesn't have to be Christmas.  I haven't branched out much in my reading lately, and I'd like some ideas for some new authors to discover.  Please let me know who you like to read to give me some ideas on what to spend my gift certificate on!