Currently there are six potential habitable exoplanets -- four of these objects have been detected in the last year, from September 2011 to September 2012. Gliese 163c is a rock-water world of 2.4 Earth radii, however, it could be as small as 1.8 Earth radii if composed mostly of rock, like Earth.
New data suggests the confirmation of the exoplanet Gliese 581g and the best candidate so far of a potential habitable exoplanet. The nearby star Gliese 581 is well known for having four planets with the outermost planet, Gliese 581d, already suspected habitable. This will be the first time evidence for any two potential habitable exoplanets orbiting the same star. Gliese 581g will be included, together with Gliese 667Cc, Kepler-22b, HD85512, and Gliese 581d, in the Habitable Exoplanets Catalog of the PHL @ UPR Arecibo as the best five objects of interest for Earth-like exoplanets.
Via Dr. Stefan Gruenwald, Ioannis