RPGClassics.com: Seiken Densetsu 3

Characters, classes, item data, spells, world map, walkthrough, and hacking guide.
http://www.rpgclassics.com/shrines/snes/sd3/

Mana World

Walkthrough, news, guides, and characters.
http://sd3.seikens.com/

The Mana Holyland

Game information, data, and strategies.
http://geocities.com/deathduelist/

GameFAQs.com: Seiken Densetsu 3

Reviews, message board, codes, walkthroughs, and FAQs.
http://www.gamefaqs.com/console/snes/game/9323.html