The Personal Code: A character personality questionnaire by Alesia Chamness.
Guide to Character Personality and Background, by Ash. A clear and simple step-by-step guide to developing a character's personality. This process leaves you with a sort of role-playing character sheet that you can bring to a game as a reference.
The Wizard's Apprentice: The life of an apprentice. Useful for a wizard's character background.
Palladin Murderers: Creating a less stereotypical palladin.
Getting in Character: I was having trouble playing a new character, so I asked for advice.
Revenge of the Gamer Chick: Some great advice for role-playing, particularly for female gamers.
Errant Dreams: This site has articles on character creation and world building.
Roleplaying Tips: A free online weekly magazine about roleplaying.
Character Sheet: 3E Wizard: A super-dense, three-page D&D 3E character sheet in MS-Word format especially for wizards, by me. Includes standard 0th level spells and a polymorph section. The most confusing parts have been filled in with example values.
Character Sheet: 3E Finesse Fighter: A super-dense, one-page D&D 3E character sheet in MS-Word format especially for finesse fighters, by me. This can be used for any non-casting class, but the armor section is reduced for finesse fighters. The most confusing parts have been filled in with example values.
Official D&D 3.5 character sheet, distributed by Wizards of the Coast.