There are loads of websites dedicated to all aspects of FFXI, so I thought it'd be useful to make a post compiling links to peoples' favourite resources. I'll kick things off with the sites I have bookmarked; comment with your own suggestions and I'll continue adding to the main post.
General
Allakhazam
One of the biggest FFXI sites out there, with player-contributed information about items, NMs, maps, just about anything. Extensive forums that should be taken with a pinch of salt.
Bilingual Website of FFXI
One of the first major FFXI information sites out there; if you need help with some of the words, try these sites.
Blue Gartr
BG's site, big forum community. If you want to hear blow-by-blow accounts of Absolute Virtue, this is the place.
FFXIclopedia
A great Wiki dedicated to the game.
FFXI Official Website
The North American Playonline site, pretty Flash elements and - obviously - the first place to look for update/maintenance info.
FFXIOnline
A long-established website, great discussions on the forums, a good source of job-playing advice.
Japanese FFXI Wiki
JP skills a definite plus!
Killing Ifrit
A site popular for its forums, but with plenty of other information too.
Koolaid Linkshell
The link above takes you to a pictoral guide of how to climb the Attohwa mountain, but the site as a whole has good FFXI info.
Linkshell Community Beta
SE's official linkshell community project, still in its infancy but sure to grow.
Mysterytour
My personal favourite site, all sorts of information and some amusing translations.
Shadow Dragons LS
A small linkshell/forum/info community.
Somepage
Really searchable site with thorough item, quest and monster databases.
Crafting, Gardening, etc.
Crafting skill up
An old-school listing of how to skill up a craft 0-60.
FFRecipe
Another guild points site.
Lokyst.net
A renkei chart, crafting timer and for you clammers out there, a clamming guide.
Pikko Pots
For all things relating to gardening, kept up-to-date.
Titanictus Guild Item Tool
Perfect for crafters, this site tells you the guild point item for the day and how many you need to make to gain maximum points, with recipes too.
Battle-related: Skillchains, Maps, Camps, Monsters, etc.
Aden's Renkei Chart
A comprehensive renkei chart, including weapon skills, blue magic, blood pacts and the skillchains they create.
Bestiary
From Vana'diel Atlas, a comprehensive monster listing.
Campsitarus
All the usual exp camps full? Check out this site to find some alternatives.
Erecia's CoP Guide
A very popular guide to CoP missions, tips for the BCs and all the cutscenes in between.
Erecia's ToAU Guide
Fantastic missions guide, sure to be updated once the Treasures sequence of missions is continued.
Nephilim Experience Guide
Charts showing experience points gain of monsters vs player's levels.
Simple is the Best.
Dynamis maps, in Japanese.
Sky Maps
An interactive compilation of Tulia maps, allowing you to trace the correct path to gods and triggers.
Skillchain Calculator
Plug in which jobs you have available, it'll spit out a renkei for your party.
Treasure Hunting Map
Another old school site, showing treasure chest and coffer locations.
Ultimate Skill Cap Chart
Ever wondered what levels your various combat and magic skills cap at? Find all the information you need right here.
Vana'diel Atlas
Maps of all Vana'diel's locations, with NMs, coffer spawns and other points of interest.
Vana'diel Monsters
Japanese skills a bonus, another bestiary.
Weapon Skill Chart
Complete skill cap listings for all combat and magic skills (numeric and "letter rank"), along with rankings and Weapon Skill info based on job.
Weapon Skill Data
Nice simple list of all WS and their modifiers.
Timers
FFXI Time Information
If you want to look up when guilds open and close, the moonphases, Vana'diel time, ferry and airship departures, and RSE schedule, this is the place for you.
MithraPride Clock
Another great Vana'diel timer.
Additional programs and edits
FFXI Dats
Custom .DAT community website - requires registration to download the .DATs, but its quick and free to do (no annoying e-mails or anything). Some good armor mods and character model alterations.
Modelviewer
A tool that lets you view character models, NPCs, equipment and even monsters outside of the game. You can also download POLUtils and FFXItool from here, useful if you like data mining.
Neko-Sentai Dats
Another .dat editing community.
Windower
Allows you to run the game windowed.
Miscellaneous
As Vana'diel Turns
FFXI Flash animations.
Bannable Offenses
Written by the notorious [GM]Dave, a look at the nooby unworld of FFXI.
Calcula's Final Fantasy Comics
An FFXI webcomic.
Castle Oztroja's passwords
A Japanese site to help with negotiating Castle Oztroja's delightful password system.
FFXI Auction House
Very useful site that allows you to check the AH without even logging into the game.
FFXI Transworld Project
An image gallery of FFXI elements meeting real life locales.
Goblin Smithy's Blog
A Smithy's Life, an off-beat look at what it's like to be a beastman.
History of Vana'diel
Excellent site detailing various plotlines in the game and the threads of Vana'diel's past, complete with screenshots.
Somepage's Fame Guide
In-depth guide to fame in Vana'diel's cities, part of somepage.com.
The Opera House
Lyrics to various Final Fantasy songs.
Title List
Curious about where someone's title came from? You'll find it here.
Warhorse Hoofprint Locations
Site for determining the location of the Warhorse Hoofprint. Once again, Japanese, but the server names and locations are in English, so usable even with no language skills.
