I happen not to read too much of AU's but this genre is totally awesome :D So, a thematic resource list, perhaps? I'll try to update this post :)LISTS
shiny_starlight has this awesome college!fic tag
majs-majs's thematic list of Merlin school stories is here
voldything has this collegefic tag
Fandom: BBC Merlin
Word count: ~11,500
Summary: Arthur, Merlin, frat brothers, the Dragon, Arthur's BlackBerry, script writing, shitty hip-hop music, Dogma, FATE & DESTINY - oh God I wish I were joking.Communications In Binary
University AU. Merlin came whirling into Arthur's life and left everything in shambles on the floor - literally. They couldn't be less alike - Merlin with his computers and his easy, goofy grin, Arthur with his breeding and his need for everything to be in it's place. They have nothing in common besides a key to the same room, but as the academic year progresses and Arthur finds himself wearing tiaras and critiquing Westlife and having picnics on his living room floor, Arthur comes to learn things about himself he didn't even know he didn't know.