one of the possibility does include 'titan' it's not a planet but one of saturn's moons because it has got frozen (i am not so sure) ammonia or methane which in time will melt and the conditions will be very much like on earth.I dont know how close it is to earth though.
There are around 50 known stars within 20 light years of earth, the nearest being approximately 4 light years away. Some are known to host planetary systems, so perhaps one of these days we'll discover an earth like planet much closer.