I like the Haven and Hearth style, where players wander and can group together informally if they so choose, or not. What I don't like about HnH is, like Travian (I think, I haven't played Travian), everybody is out to get you (mostly steal from you in HnH).
I really like building games like HnH or Wyrm, but they often tend to be unholy grindy.
There's also a setting I'd been considering for some time (although it lends itself better to a full 3D MMO than anything you pop up in your browser):
It's circa 1920, and the world has never been circumvented- the pacific ocean having never been crossed. A new continent is discovered, by way of travel west of America, which is wholly unwalked by man except for savages, and has rumors abound of gems, gold, oil and treasures from ancient civilizations. The countries of Europe and America scramble for control of the new continent, bringing with them renewed hostilities from the recently-ended great war, turning the continent into a new wild west. Aside from brigands and military foes, players are likely to face every threat that a movie has ever attributed to a mysterious deserted island- dangerous animals, dinosaurs (or other fantastic ancient creatures), cannibals, hostile flora, floods, volcanoes, booby traps, unspoken horrors and of course, fellow profit-seekers. Also Japan, which remains with closed borders to the west, is rumored to have a hold on the continent's enigmatic west coast. Most equipment comes from the east by dirigible or boat and there is enormous profit to be made in establishing mines and factories, which will produce goods far cheaper than having them shipped through America.
Players would enter the game on the east coast of the continent, as a soldier, mercenary, college professor, entrepreneur or desperado. They would be able to explore and take work from NPCs who are either from America/Europe or natives. A player's ability to get to the more dangerous and rewarding parts (farther from the shore) of the continent is dependent on their access to vehicles, and eventually on establishing camps (either as a guild or "alone" with an NPC nation/corporation) to refuel them, and to be returned to when the player is "killed" (or rather, knocked out). For clans, it is profitable to build mines or other establishments in the wilderness, but they must be able to defend them.