I did a search for "levelling mods" and "leveling mods" (because it can be spelled both ways). You wouldn't believe how many "which levelling mod is the best/should I use?" threads there are... I even found several titled "how do I beat the levelling problem?" (yes, those exact words :tongue: ).
What I did NOT find, sadly, was an in-depth comparison of levelling mods a la bg2408's magic overhaul or scaling overhaul articles. There was one link in a post from last October that linked to what was supposedly a thread with some in-depth discussion, but it's pruned.
I did, however, get a decent sense of the most popular levelling mods: nGCD, RL, and Oblivion XP (the first two are roughly equal and more popular), along with Progress. I wish I'd known what Progress did before starting my latest character... I use Arcane Archery, and it boosts your Destruction skill like mad - I hit Master by L15. Ah well...
Remember to include SPAM levelling mod as well, it′s an awesome levelling mod to us who enjoy setting the attribute points by ourselves, but natually need a system that makes more sense than Vanilla.
I've got: KCAS (outdated), SPAM, Pure Immersion, RL, nGCD, Oblivion XP, AF Leveling (outdated?), and Wrye Levelling. I'm sure I'm missing a few...
In short, Oblivion XP replaces the vanilla levelling system with a point reward system like Dungeons & Dragons style games. You earn experience points for doing stuff until you get enough to gain a level. When you level, you increase your attributes and skills as you wish, up to defined limits. The link in my sig has a more detailed description.
Thanks.
References:
http://www.gamesas.com/?showtopic=790175&hl
http://www.gamesas.com/?showtopic=820948
UESP pages on leveling mods:
http://www.uesp.net/wiki/Oblivion:Level
http://www.uesp.net/wiki/Oblivion:Efficient_Leveling
http://www.uesp.net/wiki/Oblivion:Under_Leveling
... gosh and I use to have a UESP link for recommended mods that talked a lot about leveling mods - can't find it.
bg's base mod list has a decent description of the types of levelling mods, but not really the mods themselves. Still, it's a good start. Thanks.