cough I may have a thing for this, yes? Also, bah, I realized a few of the J2 suggestions fall outside your parameters, for which I apologize, and upon re-reading Dear Neighbors is more about hot sex than a polyamorous relationship. My apologies. I highly recommend "Life Is..." regardless, even though JDM dies at the beginning of the story; it'll rip your heart out and put it together again with its depiction of polyamory, grief and survival.

* OT3'verse (http://beanside.livejournal.com/tag/ot3verse): In a fit of frustration and temporary insanity, Jensen outs himself as bi on the Howard Stern show. Jared and Jeff are there to pick up the pieces. (This link goes to a tag; there are five stories in this verse.)

* Atypical Verse (http://archiveofourown.org/series/227249): Jeff knows he's not the typical omega. He also knows thirty-seven is a bit old to be an unmated virgin. Lucky for him he's not the only one operating outside of traditional gender norms.

* True, We've Demolished a Thing or Two (http://archiveofourown.org/works/481025): The idea is simple: Save People. Hunt Things. When Sam went to Stanford, it was to save people in a different way than he was raised to. He never thought for a second that he might fall for a Hunter. Dean never thought it would be so hard to save people, but they all keep saving themselves. Jess never dreamed she'd find the perfect guy who would understand her job as a Hunter, but here she is bonding with two of them. Now if they can just keep from killing each other, it might just be true love.

* Midnight of the Century (http://archiveofourown.org/works/93252): Sam hasn’t spoken to Dean in years. He went to Stanford Law and graduated, now he is studying for the Bar and planning a wedding for the spring. He sees Dean’s fetch on Christmas in a churchyard while attending service with his fiancee' Jess and her family. Fetches are death omens for those who will die in the coming year. Suddenly, Sam finds himself on the road, looking for his wayfaring brother and trying to figure out a way for him to avoid his fate.

...I would have more, but the deli.cio.us engine is down. Again. So I can't access my bookmarks. But... this is a good start, I imagine. :)