I beat Morrowind for the first time about a year ago, as a Redguard warrior. I want to eventually finish every single quest in the game. These are the quests I know about that I haven't done yet, either because they seemed inappropriate for my character, or were mutually exclusive to other quests I already did:
Mages Guild
House Telvanni
Aundae Clan
Thieves Guild
House Hlaalu
Berne Clan
Tribunal Temple
Morag Tong
Imperial Cult
Bloodmoon Werewolf quests
Bloodmoon Carnius quests
So for each of my subsequent playthroughs, I have two goals. First, to be a different kind of character each time, with a different play style, so it doesn't get stale. My first playthrough was as a warrior, medium armor, exclusively melee weapons with maximum damage per hit, and much reliance on enchanted items, including lots of enchanter-made rings. No spellcasting, and not much use of potions or scrolls. The second goal is to do all of the quests that are appropriate for that character, including consideration to roleplaying as well as the rewards being useful for that class.
So, help me plan my next character playthrough, with these two goals in mind!