Since Progs have found a new bogeyman, the Koch Brothers, and bleat about their political contributions,
this list of the top political contributors may be handy this election cycle. It lets users who want to pick individual election cycles. FWIW, the Koch Brothers made the top 20 in the 2014 election cycle, but were not in the top 50 in 2012 or 2010. I'll bet most CCers could guess what kind of organization 4-6 of the top 10 contributors are.