I don't know the author or title. Story was on samdean archive. Sam is pissed at Dean and John for missing some school thing. He goes to a party and Dean finds him. Sam is smoking a joint while some other boy is kissing his junk through his jeans. Dean drags him out and they end up on the side of the road where Sam asks Dean if he wants to finish what the other guy started. They have sex and then Sam says something like..."Just remember you're not the only one that can deny this thing between us." It's one of my favorites and i haven't been able to find it since the archive went down.