The latest offer comes via FilePlanet. If you're a FilePlanet subscriber, you can play the first part of the game for free in an unlimited trial. The offer is good until December 31st, but as long as you download before then, your trial will not expire. FilePlanet has a limited number of keys for this offer as well.
As a bonus, anyone taking FilePlanet up on their offer will receive a free Enruned Kosalan Ring, which was previously an in-game bonus available for buying an Age of Conan ZBoard keyset. The ring offers melee, ranged, and magic damage bonuses, as well as a +1% evade chance bonus.
The offer is available to customers in North America and Europe, and can be accessed through FilePlanet.
[Edit: Apparently, this trial is available on the AoC main site as well, not just FilePlanet.]