Allakhazam.com
General information resource with database of items, quests, missions, and crafting recipes. Also contains member forums, journals, FAQs, and links.
FFXIOnline
Featuring quest, mission, and crafting information. Also has a list of linkshells and a forum.
Final Fantasy Vault
Includes news, game guides, quest information, fan works, and forums.
Final Fantasy XI
Official Square Enix webpage for U.S. players. Information on gameplay, system requirements, service and support, and multimedia extras.
Final Fantasy XI Overview
A site dedicated to Final Fantasy XI. It lists descriptions of all jobs and races. A quest and mission list is coming soon.
Juele's Online Guide to Gardening on Final Fantasy XI
Gardening information and recipes.
KoolAid Linkshell
Contains information on crafting, quests, weapon skills, and vendors.
Pyogenes' FFXI Timer
Vana'diel clock. Details moon phases, airship and ferry departure times, race specific equipment locations/times, guild hours/holidays, and magic affected by the day's element.
Shadow Dragons
Comprehensive information on jobs, quests, maps, and a bestiary. Also features game news, screenshots, and message boards.
The Final Fantasy XI Square
Provides pictures from the beta test, a list of linkshells, and a forum.