While most veteran players are probably aware of these, just wanted to give a few links for useful sites:

FFXIclopedia is one of the most useful websites. You can research items, quests, missions, find guides on job classes - everything from gearing up to maat fight and macro setups- as well as some decent guides for crafting.
Not everything here is updated; some content is dated from when level cap was 75.

FFXIAH is another great resource. You can look up items to see stats, what they are seeling for on AH, and who is bazaaring them.