Shadowlands has been the largest expansion to date. Seven themed areas, and dozens of other new locations significantly added to the game's playable area. It raised the maximum character level from 200 to 220, and introduced the perk system. Also included were a new user interface, two new player professions, improvements to the game's rendering engine, new dynamic missions, and a "flood" of new items.
Source: Wikipedia, "http://en.wikipedia.org/wiki/Anarchy_Online," available under the CC-BY-SA License.