1) An addon that marks on the map where you can find a quest giver / quest hubs.
2) An addon that grays out the parts of the map you have not been too yet (kind of like how WoW does it). This way I will know which part of the map i've been to and which part i need to discover.
I made a Reddit post about it,
http://www.reddit.com/r/elderscrolls...an_addon_that/
I think either of these addons would be incredibly useful.