Some of my favorite fic writers, some of their fics and their masterlists:
This list isn't complete by a long shot.
Gotta start with my all-time favorite, hengilas. In particular I'd recommend the Great Romances series. In this fic Kurt and Blaine have been friend-zoning each other all the way up to their first year of college where they are roommates. Lots of UST, some cheating, and well, they aren't very nice to each other for much of the story. Well written with much humor.:http://hengilas.livejournal.com/24012.html#cutid1
Whitings. Every one of her stories is perfect. In 'You Wear it Well' Kurt is on the football team and is closeted, but loves Blaine.
Sadly the above fic can no longer be found online.=(
Can't forget triddlegrl. I love her lycan fics Solace and Mangaiere:http://triddlegrl.livejournal.com/39314.html#cutid1
her consonance and dissonance series is quite beautiful
star55 (couldn't find a masterlist), she's currently writing Breathe In Now:http://scripted-star.livejournal.com/67524.html
From her list I can recommend It's Not Babysitting, and Collateral Damage.
a_rainy_monday is another great writer (really all of them are):http://a-rainy-monday.livejournal.com/58097.html
she's taken down my favorite fics but what remains is also excellent.
Over on ffnet there's Humanlikeyou. I love her D/s fics Made for Each Other and Our Place in the World. sub!Kurt and Dom!Blaine; Sebastian is also in it and has his eyes on Kurt. Trouble ensues in OPITW. Made For Each Other:http://www.fanfiction.net/s/7809930/1/Made-for-Each-Other
Our Place in the World:http://www.fanfiction.net/s/7897105/1/Our-Place-in-the-World
Only Ever His by judearaya is part of the Sons and Lovers verse. In it Kurt and Blaine have been in a relationship for about 5 years. In this fic Blaine receives a text with a pic of Kurt kissing someone else.http://judearaya.livejournal.com/2616.html
From the GKM there's Dog Days are Over by nonnygleek. It's an incomplete WIP but wonderful and has much feeling: Blaine is a dog, literally, but turns human (smut yes, but no bestiality).http://glee-kink-meme.livejournal.com/26585.html?thread=28227545
Flyblckbirdfly has many good fics. I have fond memories of her Misadventures of Teenage Boys verse. Here is the first in the series:http://flyblckbirdfly.livejournal.com/6477.html
And here is the link to her master fic list:http://flyblckbirdfly.livejournal.com/2350.html
First Klaine WIP I ever read was aelora's Together We Are the Oceans::)http://aelora.livejournal.com/1316981.html
Best badboy!Blaine fic I've ever read is rainjoy's Fix:http://rainjoyswriting.livejournal.com/126806.html?view=3651670
I can't hear Florence and the Machine's Drumming Song without thinking of this fic!
Emilianadarling's Illicit in which Kurt and Blaine smoke pot:http://emilianadarling.livejournal.com/16076.html
Alura_embrey's bondage verse fics: Disguise Our Bondage:http://alura-embrey.livejournal.com/22140.html
and Dazzling Precious Treasure:http://alura-embrey.livejournal.com/29633.html