The Normal Person (D&D 3.5): I got tired of the idea that the king's master chef also had to be able to take on half an army single-handed, so I wrote up this new set of rules for NPCs.
Starting before level 1 (D&D 3.x): Rules for an extraordinarily low-powered adventure.
Identifying Items Without a Spell (D&D 3.x): Alternative rules for identifying magic items.
Abstract Magic System (2E) (AD&D 2E): An interesting magic system, where mages have a limited amount of magical energy with which they can try to create any effect they want.
Living Magic (General)
Magical Combat (2E) (AD&D 2E): An interesting idea on making mages more 'magical' in the way they fight.
The Psionics Handbook (2E) (AD&D 2E): Having never seen the official Psionics Handbook, I wrote this up in 1995-96.
Mass Combat (AD&D 2E): A system of rules for mass combat, by The Sigil.
Custom feats (D&D 3.x)
The NetBook of Feats (D&D 3.x)