Mars,and the moon I suppose?

Venus

Venus is the closest in size and mass. That's really where the similarity ends. Though the year, day and atmosphere are very different. The day is longer than its year.

omfg it is the moon and mars. those are the only planets or masses of energy of which we can thrive on without any real problems.

There are probably planets outside our solar system that are almost identical to earth in terms of size and climate. This one is certainly closer than those in our solar system. http://www.npr.org/templates/story/story.php?storyId=9796321

1) "Venus and Mars are the most like Earth, but in different ways. In terms of size, average density, mass, and surface gravity, Venus is very similar to Earth. But Mars is the planet that is most similar to Earth in other ways. A Martian day is just over 24 hours, and its rotation axis is tilted by about the same amount as Earth's. Most interestingly, however, it is thought that at some point in Mars's past, it may have had liquid water on its surface, just as Earth does now. This leads some people to suspect that Mars may have once harbored life." Source and further information: http://curious.astro.cornell.edu/question.php?number=396 2) Outside the solar system: "Gliese 581 d (pronounced /ˈgliːzə/) is an extrasolar planet approximately 20 light-years away in the constellation of Libra. Because of its mass, the planet is classified as a super-Earth planet. Because the planet orbits in the outer edge of its parent star's habitable zone, it is thought that the planet may be similar to Earth." Source and further information: http://en.wikipedia.org/wiki/Gliese_581_d Further information: http://en.wikipedia.org/wiki/Terrestrial_planet