Fun and strategic, but free and easy games?

I don't really have the time to sit down and play on the computer for more than an hour (sometimes less) like i used to. And I have been looking for a game where you have to improve your "skills" or "technology" or even "skill points". Something where you only have to log on and choose what you would like to do, then log off and come back the next day and repeat the process. Now I don't want anything to boring, or to time consuming, just something that takes maybe an hour or less to complete the tasks on and then you don't have to sit there and worry about something going wrong until you log on the next day. If you have ever played an age of the empires game, i would like something like that, but free, online, and not as time consuming. Also I want it to be where I don't have to start new campaigns or whatever (like beating levels).