I just started trying out a new Browser MMO, I'm a fan of Browser MMO's simply because I have a slow net connection so downloading games is a pain in my rear end.
The Seventh Dragon is very similar to the Warcraft series if you have played that before.
In the Seventh Dragon you build up your castle like many other browser strategy games, making units and hiring heroes. The game has a quest system and the quests boast rewards for you and items for your heroes. the Hero system is even more in-depth than the one in Warcraft 3.
You can also create Guilds with other players.