I read this fic a while ago and can't seem to find it again. 
It was set after season five. Sam had come back and was living in the same town as Dean and Lisa, but he didn't want to interfere with  Dean's new life so he had some sort of charm that disguises him as a punk-ish guy. I think he goes by the name Prior or something like that, and he's a barista at the coffee place that Dean goes.
Edit: Thanks to aunttora for tracking it down for me!