The Hall of Countenance at the College respawns much faster than 30 days, it's more like 2! Upstairs the alchemy lab has your more rare ingredients (including spriggan sap), as well as a few healing and magicka potions. Also, the 2 barrels in the Alchemy Lab respawn with different alchy ingredients if you clean them out regularly when you do your sweep.
Two doors down is your Enchanting Room, with the respawning gems (also about 2 days).
Downstairs in the Hall of Count is a room that has a few things on the right side that are marked "take" instead of the red "steal": a gem on the dresser between the wardrobe and shelf, and a few rare ingredients on the middle shelf.
And don't forget to re-check your old room in the Hall of Attainment, as every couple of days you have respawns: the gems on the dresser, and the ingredients on the small tables on each side of the doorway.
The bad guys (inside and out) and their daedra hearts at the shrine for Mehrune's Razor respawn for me regularly. I'm swimming in those squishy things.
And it seems the briarheart guy at Red Eagle Redoubt keeps respawning. It absolutely creeps me out to see hagraven handiwork of that big patched area on his chest, and then the big gaping hole after you take his briarheart. YUK.
