From the exoplanets mailing list:

A 1.9 Earth mass exoplanet (period 3 days)
has been detected around Gliese 581 (Mayor et al).
See
http://exoplanet.eu/planet.php?p1=Gl+581&p2=d

It is the lightest planet detected up to date around a main sequence star.

In addition, the planet Gliese 581 d has a revised period of 67 days,
bringing it in the habitable zone of the parent star.

Jean Schneider

Gliese 581d is now more solidly inside the habitable zone; it was considered before to be on the outer edge of the habitable zone (this work moves its believed semi-major axis from 0.25 AU to 0.22 AU). Gliese 581d was a maybe for habitability (see this Centauri dreams article for example), depending on cloud cover, etc. Now its definitely in. The new Gl 581e is beyond the classical habitable zone.

These planets are quite close in: Rory Barnes and colleagues at Lunar and Planetary Laboratory in Arizona did some good work on the habitability of Gliese 581 c (paper online) and concluded that it would be tidally heated to such a degree it was probably never habitable. Such tidal heating might make Gl 581e habitable; time to run the model again.

Correction: On reading the ESO Press release and paper (via) it appears that Gl 581e is inside the orbit of Gl 581b, and too close to the star to be habitable. To date, planets have been labelled b, c, d .. as they are discovered, and they've been discovered shortest-period first, so 'b' also meant closest to the star. Now Gl 581e is closest to the star, with a period of 3 days.