Spell Scribing: A treatise on the materials used in spell scribing.
Creative Spell Use: Creative uses for spells, from posters to rec.games.frp.dnd
House rules for magic can be found in the house rules section.
World of Sulerin: This complete campaign world has a ton of custom spells for D&D 3.x.
Epic Metamagic: Feats designed to replace the epic spellcasting rules of D&D 3.x.