Jeffrey LeekJohns Hopkins Bloomberg School of Public Health
fivethirtyeight.com
http://www.gallup.com/
http://www.fivethirtyeight.com/2010/06/pollster-ratings-v40-methodology.html
http://www.google.org/flutrends/
http://www.nejm.org/doi/full/10.1056/NEJMon1211064