Here are a few:

Too Much, Too Young (http://www.fanfiction.net/s/5459650/1/Too_Much_Too_Young) by skagtrendy1
Summary: Sam’s been burning the candle at both ends and his family is too busy to notice.

Revenge is a Dish Best Served Cold (http://www.fanfiction.net/s/4915109/1/Revenge_is_a_Dish_Best_Served_Cold) by sammygirl1963 (http://www.fanfiction.net/u/1230513/sammygirl1963)
Summary: Sam is kidnapped and tortured by a hunter for revenge against John. Will he survive until his family can find him?

A Hiccup in Time (http://www.fanfiction.net/s/4809285/1/A_Hiccup_in_Time) by sammygirl1963 (http://www.fanfiction.net/u/1230513/sammygirl1963)
Summary: The Winchesters go on a hunt for a demigod who can manipulate time. The hunt backfires on them leaving Sammy in a toddler form with his adult mind still intact. Can John and Dean protect little Sammy until he is returned to his adult form?