Some thoughts/background/house rules I plan on implementing in my campaign:
I'm using a B/X / LL hybrid, since they're pretty much the same thing. No level caps for demi-humans. Variable weapon damage. AEC classes are in, but not available to starting characters (I might change this RC "super-classes" instead, like the Mystic). Campaign is going to be more swords and sorcery, with less magic, and pretty much every magic item (especially weapons and armour) will have a name and a story. I will be using "weapons of quality", so it is possible to have +1 weapons without having magic. "Shields Will Be Splintered" is in effect.
The idea for this campaign is very much swords and sorcery. One of the great mysteries of life will be the idea that only humans have "souls", so to speak, so only humans (and in some rare cases, wild elves, which will be explained later) can use divine magic. Dwarves were created without the influence of magic, so they have no magic ability (I was thinking of making them like the Yuuzhan Vong in recent STAR WARS literature, who are a "dead zone" to the Force, but I felt that would unbalance things too much. I am open to suggestions on how to make this work, unless I go with the assumption that PC dwarves are special to begin with, and part of that specialness is that they actually HAVE a connection to magic). Elves think they can connect themselves back directly to the first making, and as such, don't worship gods... they ARE gods. Halflings have seen what misery magic can cause, and have forsaken any desire or ability to use magic (although they can still be affected by it). Humans were created in the distant past as servants to the first races (elves, dwarves and halflings) - humanoids are the failed attempts at creating humans.
Dwarves: any dwarves ancountered outside of their mountain strongholds are either beardless outcasts, or mercenaries who have been cast out, usually for excessive bloodlust. Dwarves have no innate magical ability whatsoever - this explains their obsession with acquiring magic items, and wealth (to purchase more magic items). Dwarves worship their ancestors. Because of their lack of magical connectedness, dwarves cannot be resurrected, reincarnated or raised if killed. Furthermore, a dwarf must make a saving throw even when beneficial magic is being used on them (for instance, if a cleric tries to cast Cure Light Wounds on a dwarf ally, the dwarf must fail their saving throw for it to work). I toyed with giving dwarves a flat percentage of magic resistance, generated at random in character creation, but for now, this will work.
Elves: elves come in two flavours. High Elves are the degenerate overlords of the world, who use both swords and sorcery to impose their will. Wild elves are those who have seen the destruction their brothers have wrought, and have retreated to the wilds, becoming one with nature. PC elves will either be high elves seeking to atone for the damage wrought by their degenerate kin (or perhaps working towards some secret agenda of their sorcerous kin) or perhaps tortured martyrs, while wild elves will either be militant nature warriors, or mystic living weapons. Basically, high elves think of themselves as direct descendents of the gods, while wild elves have turned from that realization, and worship the power of nature. Because of this, wild elves may be reincarnated, but not raised or resurrected, while high elves can be resurrected and raised, but not reincarnated. I am also toying with developing a new spell list for wild elves, which incorporates some "druidical" spells, and take away a few others. High elves will need a master, just like mages (see below).
Halflings: halflings in this campaign are far more philosophical than the standard "hungry burglar" prototype. Halflings have seen the best and the worst of races, and have withdrawn from a society they see as being doomed. Kind of like Elrond in LOTR, without magic or haughtiness.... maybe more like a magic-less Galadriel. PC halflings will always be either youngsters, out on a "learning expedition" to try and understand the other races and where the world is going, or outcasts who, unlike their brethren, feel that they CAN make a difference in the fate of the world. Halflings worship ideas, rather than personifications of those ideas. Also, halflings as a race have eschewed any involvement with magic, so while it can still affect them, they choose not to use it (although they may still freely use magic items).
Okay, this is getting kind of long. More later.