Dawn of Fantasy.
This interesting MMORTS allows players to create entire armies, build up castles, and attempt to conquer the world -- and it's currently available for the masses. To promote the title, Reverie World Studios is offering the title at 33% off the normal price of $30, bringing it down to $20. Dawn of Fantasy has no subscription cost, so once you have a copy you can play indefinitely.
Reverie also extended its Dwarven Invasion promotion, in which players will receive free Dwarf mercenaries and a special quest for no additional charge. These promotions are only available for the next week, so if you're interested, you might want to get a move on. We've included the launch trailer for the game after the jump if you're looking to get a feel for what's going on in this game world.