[The Devil Will Drag You Under] by DementorDelta - Snape/Harry - NC-17 - bonding fic that is seriously CHAN and seriously HOT. A definite recommendation if you can deal with a precocious Harry and a reluctant but wanting Snape.
[The Tao of Diogenes] by The Treacle Tart - Ron/Snape - NC-17 - Snape is recovering from his injuries with the help of his mediwizard, Ron. Sounds really silly, but it works so well. There's lots of deep pain and understanding there. And sex. And a yellow duck named Diogenes.
[Making Moony Laugh] by Raven - Remus/Sirius - R - Remus and Sirius through Fred's eyes. What does it take to make Moony laugh? Warning: attempted suicide, character death.
[A Year in the Life] by Sam Vimes - Remus/Minerva - PG-13 - A different take on history -- see the events of Prisoner of Azkaban through the eyes of Remus Lupin, who is not just a teacher at Hogwarts and a friend of Harry's father, but a man falling in love with the unlikeliest of women.
[Amid my Solitude] by Sam Vimes - R - Remus/Tonks. Remus Lupin has been tapped as Dumbledore's right hand in the new Order, leader of the fight against the Death Eaters. Unfortunately he's also Harry's new guardian, fumbling his way through romance, and chasing his own heritage, no matter the cost.
[Stealing Harry] by Sam Vimes - NC-17 - Remus/Sirius. What if Lucius Malfoy got to Peter Pettigrew before Sirius Black? What if he and Remus Lupin stole Harry away from the Dursleys? Obviously an AU on the whole series. Meet an eight-year-old Harry Potter, a Sirius Black who never went to Azkaban, a Remus Lupin with a steady income, a Severus Snape who can't help liking his archnemesis' son, and a Peter Pettigrew who thinks he could be the next Voldemort... Both slash and kid-friendly versions.
[Dollhouse] by Kashuarashi - R - An old toy turns out to be the key of Draco's happynes...and sanity. Deliciously creepy Draco-centric fic with an ending that will take up residence in your brain and live there for a little while, having creepy little baby-spawn. Gen.
[Close Enough] by Helen - NC-17 - a wonderful Harry/Ron with a smattering of Neville/Hermione on the side. This is a wonderful one, folks, there's depth and complexity and emotion, things that you are usually hard-pressed to find in Harry/Ron fics which tend often fall onto the 'fluff' side of the fence. Helen's Harry and Ron are best friends and compatriots, they're real. Harry and Ron (along with Hermione, Neville, Ginny and Draco Malfoy) are working for the Ministry post-war and post-Voldemort.
[Auror Series] by Mad Martha - PG-13 - all are Harry/Ron which is so not what I usually read, but this is really good. There's a number of short stories and two long ones, One Week in the Summer which is novella length, and Circles of Power which is definitely novel length. Took a good two days to read and was hard to put down. A definite recommendation.
[Inhabited by Winter] by Yahtzee - R - Remus/Sirius but that slow, aching Remus/Sirius that makes the pairing work for me. It's set during OotP and it brings up trust, prejudices, and what really matters in the end.
[The Way of the World] by Scribbulus_Ink - R - WIP - Snape and Remus in the Muggle world. It's really quite good and totally not like the fic I wrote about the same topic. I like the take she's put on this idea. It's much more light-hearted and happy, but has that beautiful undercurrent of pain that runs between these two.
[The Proud Man's Contumely] by Kementari - it seems like an R so far, and the author says it will be a Harry/Snape, but there are also hints of Harry/Remus. I cannot reccomend this story enough: WONDERFUL characterization, strong, involving plot, and over-all incredibly engaging. Kementari has a great writing style that is very cannonish and at times it makes you ache. WARNING: WIP (but updated about once a month).
[Idle Handes] by Nimori - Harry/Snape - NC-17; a wonderful guilty pleasure wherein the manipulative Potions Master takes advantage of a naive and confused little Gryffindor. Takes place during PoA. WARNING: Explicit Chanslash, password required.
[Parseltongue-tied] by DementorDelta - Harry/Snape - NC-17; Don't let the snake assisted wanking throw you off. It's all part of the joy of the story. WARNING: Did we mention the snake assisted wanking? :)
[No Place Like] by Tara Tory - Harry/Snape, Ron/Hermione (but not the focus) - NC-17; Due to a magical mistake, Snape, Harry, Ron, and Hermione end up in Kansas. Yes, Kansas. Oh, and they have no magic. It's really very good in that 'how did anyone come up with this' way. Harry Potter does The Wizard of Oz.
[If You Are Prepared] by Cybele - Harry/Snape - NC-17; It will break your heart into a million pieces, a wonderful novel-length story about the fight against Voldemort and the developing relationship between Harry and Snape.
[The Courtship of Harry Potter] by Diana Williams - Harry/Snape - NC-17; A lovely tale about an ancient tradition with Greek/Roman origins, where a young man who reaches the age of 17 is open to be courted by an older more experienced wizard. Funny, light-hearted, with an AMAZING attention to detail - it is quite obvious the author did her homework on this one. Read now :)!
[The Familiar] by Resonant - Harry/Snape - NC-17; Incredibly original and quirky and a refreshing read. Harry turns into a frog his final year and is left in Snape's care.
[As Children Often Do] by Lux - Harry/Snape - NC-17; Takes place during Harry's fourth year, during which Harry agrees to do whatever Snape wants if he will leave Neville Longbottom alone. Harry is fascinating in this. And yes, we are all going to Hell, thank you. WARNING: Explicit Chanslash.
[Just Add Water] by Cybele - Harry/Bill - NC-17; Seamus finally succeeds in turning water into rum (or something close to it) and Harry gets good and sloshed. And then there is Bill. Sexy and naughty, two wonderful things :) WARNING: Coersion.
[Harry Potter and the Mai Tai of Doom] by Sushi - Harry/Voldemort - PG-13; Yes, you read right Voldemort. This is funny. This is really funny. Harry's on vacation and Voldemort's on vacation and much to their mutual distaste - their paths cross. Did I mention funny? :)