In my current campaign, I decided that I didn't like the flavor of a party of sword&sorcery-style adventurers (Fafhrds and Grey Mousers all) escaping from the underworld and immediately setting out for the nearest temple, where miracles and healings are available for hire. Actually, I've no doubt that Fritz Leiber could make that work, but 'miracles for hire' in such a context suggests something totally different (to me) than the D&D norm. In my Greek campaign, I was totally down with the idea that 'heroes' could buy a bunch of goats and oxen and give them to a priest to sacrifice in order to call upon the gods for some purpose. But for this campaign, it's not what I want.
So I'm borrowing some material from Beyond the Black Gate's 2009 Compendium. Low-magic healing rules for one thing, but also the 'white wizard' class. I don't really want class proliferation, but I'm okay with defining certain variants as sub-classes and split-classes. I may even wind up borrowing Jeff Rients' approach. For now, though, I'm trying something unusual with Magic-Users.
Magic-Users possess, as a result of their apprenticeship, a copy of the Common Grimoire. This contains the Eight Known Spells, the spells that every magician ought to be able to cast. A particularly promising Magic-User may be inducted into a particular tradition, being granted secret spells known only to a select few. To outsiders, a magician is a magician, and the intricacies of magical paradigms and politics are impenetrable.
The Common Grimoire
2. Detect Magic
3. Hold Portal
5. Protection from Evil
6. Read Languages
7. Read Magic
Wizards use their magic to attain and promote a harmony with the cosmos. They view one another as brethren in an order, and their magic is a subtle and constructive craft. Only a pupil who shows great wisdom will be taught the secrets of Wizardry.
The Secret Spells of Wizardry
2. Cure Light Wounds
3. Detect Evil
4. Purify Food and Drink
Sorcerers strive to master the forces of the universe. They see each other as rivals for power, and their magic is flashier and more direct than wizardry. Only a pupil with respectable intelligence can hope to comprehend the secrets of sorcery.
The Secret Spells of Sorcery
1. Cause Fear
2. Charm Person
3. Unseen Servant
In addition to the extra known spells of level 1, each tradition has its own listing of spells available at higher levels, although these are largely mysterious to a novice magician. (It's surely no surprise that the Wizard is based on the Cleric spell list with additions from M-U, while the Sorcerer spell list is pretty much the traditional M-U list with a handful of additions. In both cases, these are based on Swords & Wizardry: Whitebox edition, because I like the slimmer lists, and because I don't care for Magic Missile's effect on the game.)
I'd love to write more about this and other variations I'm implementing, but our furnace broke a little and it's getting hard to type, so I'll be getting offline and eating something warm.