Leap That Makes The Fall by miss_annthropic. AU after season 5. Dean/Cas.
Summary: With no explanation for how or why, Dean and Sam find themselves with a fallen angel on their hands.
http://miss-annthropic.livejournal.com/26490.html

Thank you very very much!

By the way, if somebody interested, I found one myself:
Redemption by ADHeaven
http://archiveofourown.org/works/404307/chapters/666711 (http://archiveofourown.org/works/404307/chapters/666711)

When Castiel brought Dean up from Hell, he lost his grace in the process and fell to Earth. Still retaining some of his angelic qualities, demons went on the hunt for him. He was saved by the Winchester brothers, who quickly learn his fall may have not have been an accident.

Edited 2014-08-19 01:46 pm (UTC)

Hi, have you read this one?

Wait and See http://fanfiction.net/s/8169946 (http://fanfiction.net/s/8169946)

No I didn't, thank you.
Is it good? I just not so fond of ff.net.

The Way Back by rainylemons gen

http://archiveofourown.org/works/488010
Summery: AU in which Dean gets between Lucifer and Cas, preventing Castiel’s death and eventual return to full-blooded angelhood. In the following months, a mostly human Cas gets a job at Taco Bell, Dean recovers from wounds given to him by Lucifer, and a silent, shell-shocked Sam wanders in from the cold.

Rock On!
Alley