I will certainly nominate Castle (which I wouldn't have thought of as small, although I'll grant that this last season has probably done a number on the organized parts of the fandom).

I will also likely nominate (as I have previously) Gargoyles and Diane Duane's "Young Wizards" series of books. I'm torn about NCIS (prime), which I followed not at all this past season given so much else running on Tuesday nights, and about Tomorrowland, which got some incredibly good stories last year but still strikes me as a very crossable fandom. And I will always think seriously about Baum's Oz books (I will get my Oz/Agent Carter story done for "Into A Bar" amnesty, though I grant that that one is proving unusually resistant to acquiring an actual plot).

I have also recently acquired a full set of original-series Star Trek DVDs, which is likely to bump my interest in that and other things Trek-ish...and I discovered just this past week that Legend (the RDA/de Lancie Western series, not the feature film) is now orderable on DVD as well.