I've got something to put in you

Title: Losers Pairing: Derek/Stiles Rating: Mature Words: 34235 Summary: Where Derek is new to college, eager to spend his time learning, and Stiles is everything he didn't want in a room mate. He's loud, he's into sports, and he keeps trying to make Derek do things.

My first suggestion would be to go to shortbusassbutt.tumblr.com

Other than that, you could try these on AO3:

Four People Ruby Seduced & One She Actually Fell For (Or: Ruby's Epic Love Affair with Humanity in General and Sam in Specific) Pairings: Castiel/Ruby; Dean Winchester/Ruby, Jo Harvelle/Ruby; Amelia Novak/Ruby; Sam Winchester/Ruby; Castiel/Dean Winchester Words: 3762 Rating: Explicit Summary: In which Ruby has a lot of sex, is not any kind of therapist that would be legal, and helps a few people out for her own reasons. (S4/S5 AU)

White Towers Pairing: Castiel/Ruby Words: 2656 Rating: R Summary: Why not be broken together? / Or, It begins like a really bad joke. She was still reeling from Sam and he was still watching Dean and they'd both been a bit lonely and on the insane side of things that night. AU Season 5.

Somehow they balance each other out Characters: Castiel, Ruby Words: 505 Rating: G Summary: Castiel and Ruby, road-tripping, eating burgers. 

The Ineffability of Chuck Characters: Castiel, Ruby, Chuck Shurley, Joshua, Dean Winchester Words: 290 Rating: G Summary: A series of unexpected encounters. [For the prompt: "Cas/Ruby. Cas finds Ruby in heaven (BECAUSE WHERE DO DEMONS GO WHEN YOU KILL THEM?)"

Season of Mists Pairing: Castiel/Ruby Words: 3389 Rating: NC-17 Summary: In which Heaven recruits Ruby, and Ruby wants to use the situation to her own ends.

Or these from blinfoldspn:

Beyond Salvation Castiel/Sam/Nu!Ruby - Bottom!Sam. Blasphemy, pegging, double penetration.

Untitled Castiel/Ruby - Ruby trying to make it violent and angry, Castiel coolly keeping it tender because it's the last thing she'd want. (This one's REALLY short though)

Title: 12 Days of Hale Publishing Pairing: Derek/Stiles Rating: G Words: 4400 Summary: Something must have poked his Christmas Spirit. It might be the way Hale was watching the proceedings with a scowl on his face, unable to hide what was clear derision. Earlier, his eyes had lifted when Stiles entered the work pen with the presents, and Stiles had been under the impression he had been vaguely pleased. The only thing Stiles could think of that would make someone such a gloomy grump was not getting a gift.

“What?” Hale asked, staring at him through the glass wall that made up the part of his office facing the work area.

“I’ve got something for you!” Stiles said, waving the small rectangular present as he walked in.

“That’s not mine,” Mr. Hale said, staring at the box like it offended him. Then he stared at Stiles like he was offending him more. “You’ve made a mistake.”

Title: Half past the point of oblivion Pairing: Derek/Stiles Rating: R Words: 4715 Summary: Stiles has a tendency to make stupid bets. It’s probably the amounts of beer he’s drunk since starting college that’s playing with his brain cells, but it seems very easy to start making bets when you’re three sheets to the wind, and then when he loses, he doesn’t like not to honor said bets. He’s kind of an upstanding guy that way.