Be aware that Big Pink sometimes likes to whump on John, and it can be a little difficult to take. Her characterisation of the brothers is usually dead on, though. I enthusiastically second Ailleann's opinions of Old Rebel Yeller and Red. Red is amazing.
Refur is like unto a goddess. No, really. You'll die either of bitter angst or laughing.
I like the baseball ones, in spite of my antipathy for baseball.
Breathe On, Sister--um. The most immediate story I may have ever read. It was more like being there than reading.
I know you said no wincest, but if you were ever going to make an exception, Bad Blood is very much in character, hysterically funny, and hot as molten glass.
For the Heavy Hearts of Soldiers, pre-series, John. A good character study and backstory, plus a how-they-met.
Don't Look Back. The little girl from Home grows up and follows in the Winchesters' footsteps.
Holy Water. Again, part of my personal canon.
Gimme Shelter. An AU where CPS takes the kids from John. A harrowing revelation why, despite his unorthodox parenting choices, they were better off with him.
On the Banks of the Tiber and its sequel, Field of Mars (linked on the page). AU fantasy. Dark fairytale, mythic and atavistic and did I say dark?
Interested in crossovers? Sometimes they can illuminate a new fandom by casting a familiar light.
Kings of the Highway, SPN/Drive.
And there's Vaznetti's 10 chapter Firefly/SPN, that starts with Zoe seeing something strange as she passes a graveyard.
There's at least one about the bracelets the boys wear, and a couple about Dean's amulet. But these should keep you happy for awhile.