I am looking for two specific stories, but can't for the life of me remember their titles.
1) After "It's the Great Pumpkin, Sam Winchester", Sam's headache gets worse and worse. Thinking it's because of the exorcism, he doesn't tell Dean how bad he's feeling until he collapses outside a motel. After waking up in the hospital, he finds out his headaches were because he had meningitis.
Edit: Found! "What hurts the most" by K Hanna Korossy
http://www.fanfiction.net/s/4914464/1/What_Hurts_the_Most 2) Pre-series. Sam is on a hunt with John and Dean on a cold night. I remember a specific issue about Sam not having gloves because he'd lost them during the last hunt, or something like that. While John and Dean are hunting, Sam ends up getting distracted by a will-o-the-wisp and lost in the forest. Dean eventually finds him by following another wisp (I think there was a blue one and a white one; one was getting people lost and the other was trying to help them? I think).
Edit: Found! "Corpse Fire"
http://dani-ellie.livejournal.com/698750.html Thanks everyone for the help!