What software is available to harvest the backlinks to a site from Google?
Google’s publicly available backlink data is incomplete and notoriously innaccurate. Therefore, a tool that harvested this info would have only nominal value. What you want to look at are companies that provide backlink data via their own methods. Open Site Explorer – which is powered by http://www.SEOMoz.org – is my personal favorite, but http://www.majesticseo.com/ is another company worth serious consideration. It used to be that as recently as October 2010 Yahoo’s Site Explorer was a good tool for looking at backlinks, but ever since the Bing-Yahoo search merger the quality of that tool has degraded. Finally, if you’re looking for backlink data on your own website, Google and Bing both offer Webmaster Tools that have this info.