Battlemaster is a massively-multiplayer browser-based online game I've been playing for a couple of weeks. It's a low-fantasy medieval warefare/political simulation. Each player is a noble and commands a small unit of soldiers (infantry, archers, cavalry) etc in the service of one of a number of realms on different continents, though you can also be a bueaucrat or trader if more peaceful pursuits appeal to you or an infiltrator if you like the cloak-and-dagger stuff.
It's designed to be the antithesis of "whoever spends the most time wins" online games, and can be played for just a few minutes each day if you like. Travel and actions take place in semi-realtime. There are two "turns" each day, representing sunrise and sunset, and each turn you get more "hours" to spend on actions up to a maximum of twelve, and travelling/fighting/whatever takes time away from your hour pool.
Your unit can shrink due to combat losses or expand from new recruits, and you and your unit gain experience and skill points RPG style. You manage the training, morale and pay of your men. Aside from conquering enemy territory in battle and defending your land from invasion, you also have to help manage your territory, working to shore up local infrastracture and cracking down on revolts by unruly peasants, loot enemy lands, challenger other nobles to duels of honor, and all sorts of other fun stuff.
Battles take place on a truly grand scale, relatively speaking. Individual nobles going Rambo and leading their merry bands off on solo expeditions to enemy territory won't have much fun. Armies composed of twenty or thirty or forty units moving and fighting as one is the norm rather than the exception. Each realm has leaders selected from among the playerbase, with the form of selection varying on the type of government system (republic, tyranny, etc.).
The main game page is http://www.battlemaster.org. There's a game wiki with a good deal of useful information.
If you decide to give it a try, I recommend you choose the Atamara continent and either Tara or the Cagilan Empire as your realm allegiance. I started with Tara and then went over to their ally the Cagilan Empire.
Tara is still the smallest realm on the continent, but they're up to five regions from a low point of three and have survived combat with the realms of Carelia and Redspan, and the treacherous realm of Falasan on their northern border, which stabbed them in the back when they were at their weakest. A lot of guys I know from another forum play for them. I started with Tara, but I didn't care for the leadership and what I felt was a lot of internal bickering, so I jumped ship to the Cagilan Empire, their ally. The Empire is a lot bigger and in my opinion more easy-going and better led, but Tara needs the players more than the Empire does.
We're currently engaged in a long campaign against the realm of Carelia to the south. Tara has taken the regions of Craigmore and Ledunds from the Carelians, and a combined Taran-Cagilan force has overwhelmed and defeated the Carelians at the city of Skalk, which they took from the Empire before I joined but which will revert to our control any day now after the rout of the vastly outnumbered defenders. The Carelians tried to counterattack into the Taran region of Tandsu but were defeated in a pitched battle between two relatively evenly-matched armies this morning. We Cagilans are anticipating orders to move against the Carelians and their allies from the realm of Redspan soon, possibly when the takeover of Skalk is complete.
If any of the above sounded interesting to you, come check it out.