I've come across some other sites featuring /d/-related content you can read. I figure, since they're "other stories", this post belongs in this forum.

Shokushu Campus - Tentacle monsters raping schoolgirls. Also check out the Shokushu Campus forum, where people are always roleplaying! (They have some rules about content, though; no impregnation or bestiality, for example.)

Tentacle Rape Forums - Lots of roleplay and a few stories here, too. Not many rules except "don't harass each other". And there's an imageboard!

Monster Girl Unlimited - These are the guys who translate the monstergirl profiles. There are also a bunch of people writing stories.

Anyone else got any links?

well I've found a choose your own story site that's pretty good so far

http://www.chyoo.com/

Hm, intriguing! I suspect a lot of the stories are incomplete, but...