In just a short few hours, anyone who has ever had a paid FFXI account will be able to login for free for an entire week. To kick off this adventurer appreciation campaign, Square Enix has XP bonuses in affect, brought back the Dragon Quest and FFXIV: A Realm Reborn crossover events, has made available previous limited time only trusts, and prepared this video from Dr. Shantotto herself on getting reacquainted with Vana’diel.
Also be sure to check out the handy adventurer primer (recently updated and mobile friendly), which should help you plug back into where you left off.