I've never really gotten into that side of modding. Any recommendations?

Anything made by Simyaz. They're all companion mods, but they all come with amazing quests.

Bartholm

The Lost Spires

are two that immediately came to mind. I haven't played OB in ages, and there are some excellent mods out there. I am sure others will have recommendations

Windfall is another good one.
Cybiades is another one I've heard of, but haven't yet started.
Kragenir's Death Quest is really cool as it integrates into the characters of vanilla Oblivion. On the same note, integration: The Stranded Light is one of the most lore-friendly mods touted out there (I haven't started it substantially to vouch for this yet).

Those look really cool. I'll have to give them a try some time.

Ayleid Steps
Verona House: Bloodlines (get the debugged version though)

Also depends on whether you want the mods to be JUST quest mods or if you're also looking for mods that have other purposes that also have quests in them.

meh, I really just meant questlines