We have only found one planet with similar size to Earth within the habitable zone of its system and star.
However, scientists estimate there are at least 40 Billion Earth sized planets orbiting in the Milky Way Galaxy alone. See my link provided in vote above for this article.
Hey thanks for the info, however, these are not Earth-like planets. In the NatGeo you site, they actual note that those 8 planets are "less than 2.7 times the size of Earth". They then go on to discuss a bunch of new possibilities they may have found, etc. etc. etc. Currently, the only Earth-like planet, meeting requirements outlined, that is being deemed Earth-like, inhabitable, and realistic, is the one mentioned previously.
However, keep your eyes peeled, they update that info every day so you may find something new :)