We are using mostly 1st edition AD&D rules in the Eternal Warriors pbem, with some variation.

House Rules

Magic

Range, duration, casting time, and area of effect of spells are used. Material components are typically only used to limit spells for story or plot effect, and for the most part you don't have to worry about them. Gestures and incantations are almost always required, depending on the spell description ("somatic and verbal components"). Spells must be stated before initiative, and can be interrupted during melee combat. If a spellcaster is hit in the process of casting a spell, an intelligence roll may be allowed to see if he or she completes the spell, depending on the circumstances.

Plot Point Use: A plot point can be spent to alter the effects or requirements of a spell. Some possible changes: increasing the range above what is listed, reducing casting time, performing it without gestures, automatically being allowed to cast it after taking damage during casting, altering the special effect (changing lightning to fire, e.g.).

Combat

To determine initiative I roll d6 for each side, no modifiers (lately we've been doing individual initiative). To hit is determined by the attack matrices, reproduced below. Damage is by weapon type, plus modifiers like strength, magic, weapon specialization. Natural 1 to hit is a fumble.

A natural to hit roll of 20 is a critical hit, and the target must save versus death or die instantly. If the target saves, double damage results. This is double total damage, so modifiers are effectively doubled too.

A character is unconscious at 0 hit points. At negative hit points, the character loses one hit point per round. At the end of the round with -10 hit points, the character dies.

If a character takes more than 20 hit points of damage in a single shot, the character may be knocked back or stunned or both. I may allow a CON roll to avoid the stun or a DEX roll to avoid knockback.

Ability Modifiers

Abilities have modifiers equal to +1 for every point above 14, making 18 the normal human maximum with +4. The trend continues thus, so 19 is +5, etc. Fighter Skills

Fighters gain skills with weapons they commonly use. Every even level, fighters gain +1 damage with a particular weapon class. Classes are, for example, sword, axe, spear, polearm, unarmed combat, bow--fairly broad. Fighter subclasses get half this bonus, or +1 every other even level(!).

Skills

Skills a character should have or attempts at other skill-like acts require a skill roll. This excludes thief skills, which use the PHB rules. The skill roll is

To perform a skill, roll the skill rating or less on 3d6. Experience adds to your skills, and I may award points to your existing skills if you used them during the adventure. The skills do not limit what a character can do, they are just things the character can do better than normal.

Following are some useful links:

Attack Matrices for all classes. They are replacing thAC0, though they are nearly identical.

Attack Matrices for monsters and Saving Throws for all classes.

Other Tables such as encounters and invisibility