All MMORPGs develop a community atmosphere as they mature - some more than others, of course. However, few MMORPGs design tangible in-game benefits into their social systems (beyond guild chat/bonuses). Warhammer Online boasts interesting guild bonuses in their banner/standard and guild leveling systems. Many MMORPGs (like City of Heroes) allow guilds to construct their own unique bases or guild halls. Some games (especially the Free-To-Play ones) post leader boards for bragging rights. Advanced crafting systems in other games are heavily social in their interdependency dynamics. While all of these systems are fantastic, Atlantica offers some unique and interesting Community options.
You can read the full and detailed overview here. Enjoy!