The Infinitizers.
The Black Book of Love and Pain...

http://www.asianfanfics.com/story/view/35907/my-secret-nerdy-boyfriend-gangs-infinite-kimmyungsoo-korean-myungsoo-you

another L story. i haven't read it yet but i think it's quite good ^^

http://www.asianfanfics.com/story/view/197608/the-presidential-son-infinite-myungsoo-you-exok-kai-sehun

one of my personal favourites starring L ^^ this story have sequels too.

Uh my favorite fic which is still on going is called Her Blood Whispers Fear (not a vampire fic). Also fashionchik91 and KatingaTrouble have some amazing stories.
This was also another of my favs: http://www.asianfanfics.com/story/view/98582/the-girl-who-can-t-break-up-and-the-boy-who-can-t-leave-angst-infinite-myungsoo-woohyun

I hope you can read my ff ^^ I'm new here~