Check this out: There may be more Earth-like planets right here in our own Solar System, out on the edges in the Oort Cloud. From BBC News:

Rocky planets, possibly with conditions suitable for life, may be more common than previously thought in our galaxy, a study has found. New evidence suggests more than half the Sun-like stars in the Milky Way could have similar planetary systems. There may also be hundreds of undiscovered worlds in outer parts of our Solar System, astronomers believe. [via io9]
 

I’d love to see some stories that explore this idea. (Hint, hint.)