Let's hear it for well-written slashfic!!
The List by cha in saucyminxfix - Slash, wincest. Long romantic fic in seven parts, AU set in season 3. Dean and Sam coming to terms with Dean's deal.
This is just the most BEAUTIFUL, well-paced, well-written fanfic. The wincest was handled really well, not rushed into like a lot of fics seem to do. The emotions surrounding it all were very believable, and the progression of the relationship is slow and careful and every step is exquisitely detailed.
WARNING: The emotions in this story are strong and realistic and you will be pulled along with it. There is a lot of poignancy in this story, so be sure you're in the mood for an emotional rollercoaster ride before reading. Because the writing is THAT GOOD.
I cannot put into words how much I love this fic. Really, I can't do it justice. That makes me a little sad... :'(