If I wrote some really, really niche fiction/fanfiction, where could I put it that you guys could easily read it?

Niche in what way?

I'm going to go out on a limb and assume it's hypnosis/MC themed. If that's the case, then I recommend MCstories.

www.mcstories.com/index.html

EMCSA doesn't accept fanfiction anymore. You could always put it up on dA or Pastebin, or maybe AFF, although depending on how "niche" it is I don't know if it would stay up at any of those places (I don't post fanfiction anywhere so I'm not speaking from experience here.)

If it contains underaged main characters you could submit it to Piper's Domain

www.asstr.org/~Piper/index.html

If they were images and not fics they would be tagged as follows (spoilering so not to thoroughly ruin the surprise for everyone):
Fic: bondage corruption female_to_futanari_transformation femsub foreskin happy_trance hypnotic_eyes kaa_eyes mind_job mind_rape panties penis_in_panties resisting tentacle_job tentacle_rape tentacles
Fanfic: accidental_hypnosis accidental_mind_rape cum cum_everywhere cum_explosion ejaculation female_to_futanari_transformation foreskin futanari_to_female_transformation gardevoir happy_trance heart_eyes hypnotic_eyes hypnotized_hypnotist masturbation mind_job mind_rape mirror pokemon self_hypnosis

These were basically an experiment in how far I could go without hitting the hard stuff like gore and vore. It isn't the kind of thing I'd like to be known for writing, but I figured someone here might enjoy it nonetheless. Posting on dA is out of the question.

Also, sorry for the late reply. I had to leave for work far earlier than expected.

What's a <<www.craveonline.com/image...iracy-keanu-dinosaurs.jpg|mind_job>>?

That's where the dom uses hypnosis to sexually stimulate the sub, usually to orgasm.

Found a place to host them temporarily.
Fiction: freetexthost.com/agidhjerlz
Fanfiction: freetexthost.com/yn1h30wcbw
Links will expire in three days.
Password to view them is: hypnohub

Wait, passworded, obscure service that deletes in 3 days?

May I recommend <<pastebin.com/|pastebin>> instead, for a text-only host?

The password and expiration date were optional. I'd be willing to remove the expiration date if there's actually interest in these niche lemons, but the password stays. I was able to google into a very vanilla erotic short story from this site, and I don't want these getting google famous.

I sincerely doubt you would be able to find your own story easily just by having it on pastebin, but in any case it provides private pastes, which won't get listed (and won't be thus searchable). Though I don't see why you would want to keep them out of searches' reach...