These are not very long, but you might find them interesting. One is from season six, and one is an AU of the ending of season six. They say Dean/Cas, but it is really only implied, not anything really in the story. The first one is funny, and the second is very serious. I enjoyed them both and I hope you do as well.

Pila Jectus - Summary: Dean and Sam find a strange object that seems to have something to do with angels. http://shane-mayhem.livejournal.com/327718.html

Mercy of the Fallen - Summary: Castiel returns to the prison after the events of 6x10. http://shane-mayhem.livejournal.com/301972.html

These are by different authors.

Something Primal - Summary: Castiel turns himself into a dinosaur to save the Winchesters from an escaped zoo of demonic animals and save a seal (66, not an animal) in the process. And then things get weird. http://archiveofourown.org/works/164335

Hail Mary - Summary: Take one newly human ex-angel on the run from Heaven. Combine with one mysteriously resurrected and increasingly pissed off Mary Winchester. Add overtones of Apocalypse. Shake well. http://archiveofourown.org/works/1023413/chapters/2036435