I've been using this for some time. Now i think its tested enough to release...

http://oblivion.nexusmods.com/mods/42742/

Need OBSE (done with v20)--> http://obse.silverlock.org/
done with SI instaled. If it doesnt work with vanilla Oblivion, point out, I can look into it at weekends (but hope it works...).
Tested and compatible with MODs/overhauls that change spell stats/schools/mastery levels like OOO or LAME. Does not matter if a spell have its name changed, school changed, mastery changed... ASLES checks in game the actual stats of the spells when needed.

DESCRIPTION
ASLES is a MOD (game MODifier) that allow you to naturally learn new spells.

Do you belief your char should learn Spells by him/herself? This MOD is for you.
The world have magic in everyplace you go: monster are born with it, farmers use it all the time, just as any bandit/guard/townfolk. And yet, even if you are the greatest hero (are you something else?) of all times, you only learn new spells by "buying" 'em? I cant belief it!!!! Can you?

Now you can learn new spells by casting spells, by exercise, by growing your magic abilities... Your intelligence affect how often you'll try to learn/develop a new spell - in case of sucess you'll have a new spell added to your spell list.

You dislike the way I put it? Lets try a different approach:

Imagine a divine magic wheel with all the spells that the divines can grant someone. Each time you cast a spell, you'll be judged if are worth to learn something new. If you are worth, and If the wheel points to a spell that you have the necessary skill level (Novice/Apprentice/Journeyman/Expert/Master) in it's school (Alteration/Conjuration/Destruction/Illusion/Mysticism/Restoration), you will be granted it. Not even the divines would grant a novice in restoration a master spell, right?

How it really works: a script runs each x seconds, the higher your intelligence the more often it'll run. If you are casting a spell when it run, one of the Oblivion Spells will be selected at random. It'll only be given to you if you have high enough mastery level in it's school.
So... a warrior can learn something eventually, because restoration/alteration/illusion/anything can be used as suport for your char, and a mage shall learn more because it use spells all the time. But because because aspell your char cant learns can be choosen, the spells you'll learns should be rare.

How to install: extract the plugin ASLES.esp to your Oblivion/Data folder, and tick it with your mod manager of choice...

Incompatibilities
Should have no incompatibilities: It works with unique named hidden quests, unique named scripts and unique named variables. Zero chance to override something. It changes nothing from Oblivion, and adds nothing to Oblivion World. All quest spells are excluded, just like Finger of the mountain, Essency Drain and Wizard's Fury.
Can be placed anywhere in your loadorder.

OBS1: if you find some spell that should be removed, for any reason, please point it.
OBS2: This mod causes no bloat. Can be installed/Uninstalled anytime, with no traces left other than the spells you have (maybe) learned.
OBS3: You can even forget you have ASLES... its was done to blend into the game, and only rarelly you 'll remember its existence. If you cant even tell if ASLES works, temporary install ASLES craziness. cast something like 30-50 spells. See the mod working. Unninstall it again.

hope you enjoy this mod as much as I have been enjoying.

PS: technically I could make something similar to any spell list from any mod, but wont do it because its not the author vision. Please dont bring it up (unless you are the author, but in this case you are free to use and adapt these scripts as your own, unless you really want me to do it).

Tnx bethesda for this game - I come back every year, even if theres something else to play.
Tnx all modding community - all times I came back, there was a new Oblivion to live and feel
Tnx to you for spending your time to read all this.