Amalthia's
Fanfiction ebook library has a lot of great reads; everything I've read from there was excellent.
I read a lot at the
Archive of Our Own (AO3), which has a higher quality of writing than most multi-fandom archives because it was founded by a swarm of fannish authors who wanted a stable archive ("we need to own the servers!"). The archive's still in beta testing, and the code shifts around occasionally, but most of the fic is excellent. (Eventually, the average quality will drop. Right now, the archive is mostly known by experienced, *good* fanfic writers.)
Got a flurry of Marvel fanfic recs at my Dreamwidth recently;
http://elf.dreamwidth.org/295822.htm...422#cmt4417422
Harry Potter I can go on for *days* about. A while ago, I put together a list of
20+ Snarry Recs; the first 5-6 are novel-length. And there's
Painless J's Harry Potter Recs, both standard "quality" recs & themed lists. I've also used the
Snarry Reader at Livejournal to find recs. (I could probably find some less, erm, problematic recs. I've read a smattering of Harry/Draco and occasionally even some genfic.)
Recent Trek:
Seperis'
You'll Get There in the End (It Just Takes a While) and sequel
War Games are great.
Deastar's
So Wise We Grow, also.
All of
Mijan's Trekfic is excellent. (So is her
Harry Potter fic, but as much of it is Harry/Draco non-explicit, I haven't read it all.
Eclipse is wonderful.)
Older Trek: Killashandra's Turning Point series (
Turning Point,
Full Circle) were among my favorites when I first found online fanfic.
CM Decarnin's
Intreat Me Not To Leave Thee is great--if your tastes run to brutal & explicit. (And a particular type of wordy which I love, but other people have said bores them. YMMV.)
SGA would take me a while to round up--I haven't watched the show; I just know lots of fans of it & so I see recs floating around. I don't have any that come to mind at the moment.