Thus far we have an unconfirmed report that Gliese 581g might be rocky (since it may be too small to be a gas giant - although the mass given is a minimum figure) and that it seems to be in the right 'goldilocks' temperature zone for liquid water - that's if there is any water there and if the atmosphere is of the right composition!I think we should pay Gilse 581g a visit.
Of course, the phrase 'Earth-like' is being used with some lattitude here: the gravity on Gliese 581g is higher than on earth (because its about three to four times the size of Earth). Moreover, the planet is 'tidally locked', meaning it doesn't rotate (i.e. no seasons). This probably means that there's only a narrow 'twilight zone' of the planet that's even potentially habitable; assuming, of course, that the atmosphere (if it even has one) hasn't frozen out over time to the night side of the planet!
ID.Plus: Glise 581g - first 'earth-like' exoplanet?