Question: Some fantasy RPGs treat magic as arcane and thus rare, possibly subject to suspicion by the masses. Other games treat magic as somewhat more prevelant but not ubiquitous.

At some point in this trend, magic may become so commonplace as to be considered a commodity.

**What published fantasy RPG and/or setting features this level of magic?**

One criterion: The magic affects ordinary commonplace people multiple times on a daily basis (i.e. not just adventurers and not just occasionally).

Also: What major socioeconomic characteristics are a direct result of this degree of cultural permeation?

(See Heinlein's novella *Magic Incorporated* as an example of such.)

Answer: 
**Planescape** is another great example, although in this case it is less about a "standard" fantasy world with a lot of wizards, and more about a world where **everything** is supernatural.

Sigil, the main city of the setting, is filled with portals to other fantastic places. Below are some of the ways this setting and its level of magic affects people day-to-day:

* Almost everything in Sigil is imported through the portals. Because of this there is massive amount of imported minor magical trinkets.
* Most citizens in Sigil are aware of portals and how they work, and while this isn't spellcasting, fast travel through those portals is the basis of most local trade.
* The demographics of Sigil have been heavily affected. Rather than a city that is mainly comprised of non-supernatural beings, there are huge populations of things like imps, demons, angels, fey, and other more exotic creatures. A citizen would see dozens of innately magical creatures throughout their day.
* Because of commonplace magic, the residents have access to a lot of simulated higher technologies like water purification, heating, cooling, steam-power and the like.

Overall, this level of magic does impact the lives of everyone in city, and does raise the socioeconomic level of many citizens. Rather than living a dark age equivalent existence, you're really going to see something a bit closer to a Victorian era- there is still an underclass, but the economy is more about trade and production than it is about subsistence.
Just thought of this a bit ago, but I'd like to offer 

**[Cthulhutech](http://www.cthulhutech.com/)**

Ever since the re-emergence of the Great Old Ones and the war with the Migou/Nazzadi, magic is pretty common, though heavily regulated by the government. Spells have a Power/Legality ratings, and sorcerers are required to be registered with the government. Magic in this world doesn't have the ability to power trains or anything like that, but a couple of examples of how everyday people encounter sorcerers/magic (I'm working from memory so the rankings might be off a bit):

* Sex Change operations have totally been replaced with a spell that changes genders, replacing the need for a costly operation (Rank 1 spell, legal with license, illegal to cast on the unwilling)
* Personal Defense is covered by a Sphere of Woe, essentially a spherical taser that floats around your head. (Rank 1, Legal with license)
* There is a ritual to locate people/items that have been lost (Rank 2, Legal with clearance)
* Several Warding spells to keep various people/robbers/extra-dimensional horrors out (Varying Rank/Legality)
* One could conceivably find Elder Signs all over the place.

As such, government investigation and law enforcement typically keep a few sorcerers on the payroll, and normal citizens can get access to various spellbooks (many redacted to keep the sanity-bending contents out of normal hands).

Edit:

As @Mirv120 points out, Cthulhutech also has high-tech which is powered by magic. The D-Engine is essentially a magical device which caused all of its creators to go insane, but enabled the use of giant mechanical suits and near limitless energy. Not to mention the Engels are giant monsters encased in armor.