I'm finally getting back into Oblivion after a long absence. I've got all the essential mods installed, I'd just like to know what the newest mods are that are a must have? Preferably looking for quest/creature mods.

List of lists:
http://www.gamesas.com/index.php?showtopic=1010109
Top 100
http://www.tesnexus.com/downloads/top/alltime.php
Files of the months:
http://www.tesnexus.com/downloads/filesofthemonth.php
Hall of fame:
http://planetelderscrolls.gamespy.com/View.php?view=oblivionmods.HOF

List of topics exactly like yours that have already been answered: (You can also find my favorites in post #4)
http://www.gamesas.com/index.php?/topic/1072579-the-any-mods-list-of-topics/

If you want any further help I suggest you tell us about yourself; what you like and what you're looking for... Here's some questions to get you started:

Have you played Oblivion already?
What sort of things interest you?
What type of Character do you usually play? (good/evil, theif/mage, roleplayer/random-no-story-hack-and-slasher?)
Are there specific types of mods you think would interest you? (Quests, graphic mods, gameplay mods, overhauls, etc.)
When did you leave?