The people at Information Is Beautiful created a very interesting visual representation of the worlds biggest data breaches found HERE. The criterial to make this list is being a company that experienced losses greater than 30,000 records during a data breach. Each bubble represents a company and can be clicked to bring up data about the breached as well as a link to the original report covering the incident. The next examples show clicking the recent Home Depot breach to pull up the quick info and detailed article. There is a filter on the right used to tune into what you want to view. Pretty cool little tool.
Another good source for learning about data breaches is the Verizon 2014 data breach report. I wrote about this and included a link to the report HERE.