There have been novella anthologies on many themes and for many holidays, but Christmas novella anthologies blow all the rest out of the water.
A novella is usually defined as between 20K and 40K words, so it's more than a short story–it's long enough to have character development, a proper romance, and a plot. Christmas, with warm fuzzies and over the top sentimentality, is perfect for novellas. <G>
Those of us who started out as Regency writers at NAL tend to have written more than our share of Christmas novellas–I certainly have! I've collected mine into two different collections: CHRISTMAS REVELS, with five novellas, and CHRISTMAS CANDLES, which has two novellas.
But today's riff is because I've produced two of the stories from Christmas Revels as standalone e-books: The Christmas Cuckoo has been available as an e-book for several years, and I quite recently produced an audiobook version which is available for a very modest sum.