Rec lists
I've deciced to channel my fandom energy in a worthy cause and start recing things! First things first, I will start with recing rec sites! This makes my OCD otter happy (he likes order, okay?) and besides you can never read too many rec sites. These are the glorious sites that helped my navigate the fandom and find so many, many truly remarkable stories. So credit to them!
Later on I’ll start reccing my own faves, but of course taste varies, so check out everything.
General Rec Sites
Rhaegal's Recs
With nearly 500 recs this is the biggest K/S rec site in existence. It’s also the best. You can actually filter for rating, relationship status and pairing (most is K/S, but you can search for others as well). In addition, you can specifically filter through a ton of story tropes, looking for the one you’d like to read (academy era? Infidelity? Shoreleave? TENTACLES?). Threesome pairings, RPS and vids are also recced, along with a small part of other slash pairings. Rhaegal is nothing if not thorough, and her taste is f-l-a-w-l-e-s-s. You can read the rec list on dreamwidth as well if you like that better (there it’s already sorted according to different story types). The dreamwitdh site doesn’t get updated anymore, but if you haven’t read a lot in this fandom, this is probably the best place to start. Favorite stories are labeled by Rhaegal.
Avictoriangirl's Recs
This rec site is also plain amazing! You get a megaton of wonderful recs with detailed comments, presorted by story types. Also, as an additional bonus, you have a twin rec entry for the Kirk/McCoy fans - equally as long and well done! Vids are also recced. And: avictoriangirl has a subsection for "Epicness", which are stories that are just...epic (oh, I know, you didn't see that twist coming!).
NEWCsad's Recs
Wow! I just discovered this absolutely amazing, extensive rec list! The recs are listed by tropes here - and you've got about 30 - 40 to choose from! That must have taken lost of effort (I'm awed). Go check it out!
Aznara's Recs
Beautiful, extensive list of K/S recs (and RPS too, if that's your cup of tea). Unsorted.
Debora's Recs
Long list of 100+ recs, sorted for different types of stories.
Terra-Lilly's TOS Recs and Reboot Recs
Long, wonderful lists for both Universes, not sorted for story types.
Anyuemugetsu's Recs
Mixed list of recs, unsorted, features also recs for rec sites.
Votaku's Recs
A mixed bag of K/M, K/S, K/S/U, gen, RPS...
ST Reboot Recs
Various pairings, meta, gen and vids.
Judithly's Recs
Mixed list of K/S and K/M, Reboot and TOS (though way more AOS, all in all).
Irisbleu's Recs
Mixed list of recs, unsorted.
Start Trek Classic Slash Fiction
Lots of TOS recs, most dated to 2003/2004 (so not the really "old" classics).
Specific Rec Sites
Ratcreature's AU recs
If you love AU as much as I do, you'll love this site. Check it out!
Acidqueen's Kinky Corner
Let's just say it's not a poetry reading you're getting here. I only recently discovered this TOS-based smut fest, so I can't vouch for the quality of the stories, but if you're looking for roleplay, BDSM, prostitution or general kinkiness, this seems to be the place to go. You'll find every Trek series represented (not Reboot Trek, though). Accompanying images on this site are NSFW. Some of the stuff is too dark for me (personally), but I can't speak for other people's taste.
Fandom Sites
Fuck Yeah Kirk/Spock
This tumblr is closed, but still serves as a pretty amazing archive for K/S slashers.
Fuck Yeah Team Jones
A tumblr for your daily dosage of Jim and Bones.
Futures Worth Remembering
This tumblr is a treasure chest for all things fandom-related and specifically for all things involving Kirk/Spock (and their undying love for each other).