Ogame.org is a web-based resource management strategy game. You start off with a few resources in your pocket, enough to build a Solar Engery Plant and a Metal mine and you are off and running.
You can work your way up to building spaceships of all sorts, planetary defense shields, missles, espianage probes. You can attack planets and steal resources. It's real-time but generally slow as you ramp up your empire. It doesn't require a lot of attention and can be fun if you like the idea of "leveling up".