Oooooh. Lovely. And I see loads of my own personal old favourites have already been suggested.
With one eye on the coming season <g>, a short but very cute and sweet story which I love reading around this time of year is Gina Blank's
Have A Jolly Holly Christmas...Or Not JoMarch's three little vignettes are not to be missed imo.
I love Carol Malo's Recognition series and Margaret Brignall's stories. Especially her trilogy about Clark's early life. (ETA: See these have already been mentioned - ignore me.)
Peabody's
Goodnight, Metropolis is a sweet little next gen vignette.
Anything by Shayne.
Ack, I hate this.

I wish my memory was sharper these days. I know I've forgotten tons of terrific stories.
I'll be back if I can remember more.
LabRat (who used to have a handy index for this kind of thing with all her favourites on it...)