Gliese 581
If the six-planet model is correct, then at least two of the planets might be habitable.  In other words, humans might be able to live there.  In this model, the planet 581d orbits at the outside edge of Gliese 581's habitable zone, and the planet 581g orbits in the middle of the habitable zone.  If the atmosphere on 581g is like Earth's atmosphere, the planet's temperature would be between 236 and 261 Kelvin (-37 and -12 Celsius, -35 and 10 Fahrenheit).  This is only a little lower than Earth's temperature.