The Settlers: Rise of an Empire has been released as an open beta, containing one single-player mission, online and LAN gaming capabilities. While there is no 'free-roam' type game in the beta, you can start a LAN game with just yourself, instantly win, but choose 'continue playing' and enjoy building up your empire with only a few bandits to bother you.

Open Beta on Gamespot (requires free registration)

It's looking to be a very interesting game so far, with the best aspects mixed in from the previous games in the series. It's a real change for me considering I usually play Command and Conquere, which is solely about combat buildings and an economy. The Settlers: RoaE focuses much more on the fundamentals of an empire, with various primary (collecting) and secondary (processing) industry buildings, as well as entertainment and cleanliness providers (broom-makers, heh).